manpagez: man pages & more
man perl5220delta(1)
Home | html | info | man
PERL5220DELTA(1pm)     Perl Programmers Reference Guide     PERL5220DELTA(1pm)




NAME

       perl5220delta - what is new for perl v5.22.0


DESCRIPTION

       This document describes differences between the 5.20.0 release and the
       5.22.0 release.

       If you are upgrading from an earlier release such as 5.18.0, first read
       perl5200delta, which describes differences between 5.18.0 and 5.20.0.


Core Enhancements

   New bitwise operators
       A new experimental facility has been added that makes the four standard
       bitwise operators ("& | ^ ~") treat their operands consistently as
       numbers, and introduces four new dotted operators ("&. |. ^. ~.") that
       treat their operands consistently as strings.  The same applies to the
       assignment variants ("&= |= ^= &.= |.= ^.=").

       To use this, enable the "bitwise" feature and disable the
       "experimental::bitwise" warnings category.  See "Bitwise String
       Operators" in perlop for details.  [perl #123466]
       <https://rt.perl.org/Ticket/Display.html?id=123466>.

   New double-diamond operator
       "<<>>" is like "<>" but uses three-argument "open" to open each file in
       @ARGV.  This means that each element of @ARGV will be treated as an
       actual file name, and "|foo" won't be treated as a pipe open.

   New "\b" boundaries in regular expressions
       "qr/\b{gcb}/"

       "gcb" stands for Grapheme Cluster Boundary.  It is a Unicode property
       that finds the boundary between sequences of characters that look like
       a single character to a native speaker of a language.  Perl has long
       had the ability to deal with these through the "\X" regular escape
       sequence.  Now, there is an alternative way of handling these.  See
       "\b{}, \b, \B{}, \B" in perlrebackslash for details.

       "qr/\b{wb}/"

       "wb" stands for Word Boundary.  It is a Unicode property that finds the
       boundary between words.  This is similar to the plain "\b" (without
       braces) but is more suitable for natural language processing.  It
       knows, for example, that apostrophes can occur in the middle of words.
       See "\b{}, \b, \B{}, \B" in perlrebackslash for details.

       "qr/\b{sb}/"

       "sb" stands for Sentence Boundary.  It is a Unicode property to aid in
       parsing natural language sentences.  See "\b{}, \b, \B{}, \B" in
       perlrebackslash for details.

   Non-Capturing Regular Expression Flag
       Regular expressions now support a "/n" flag that disables capturing and
       filling in $1, $2, etc inside of groups:

         "hello" =~ /(hi|hello)/n; # $1 is not set

       This is equivalent to putting "?:" at the beginning of every capturing
       group.

       See "n" in perlre for more information.

   "use re 'strict'"
       This applies stricter syntax rules to regular expression patterns
       compiled within its scope. This will hopefully alert you to typos and
       other unintentional behavior that backwards-compatibility issues
       prevent us from reporting in normal regular expression compilations.
       Because the behavior of this is subject to change in future Perl
       releases as we gain experience, using this pragma will raise a warning
       of category "experimental::re_strict".  See 'strict' in re.

   Unicode 7.0 (with correction) is now supported
       For details on what is in this release, see
       <http://www.unicode.org/versions/Unicode7.0.0/>.  The version of
       Unicode 7.0 that comes with Perl includes a correction dealing with
       glyph shaping in Arabic (see
       <http://www.unicode.org/errata/#current_errata>).

   "use locale" can restrict which locale categories are affected
       It is now possible to pass a parameter to "use locale" to specify a
       subset of locale categories to be locale-aware, with the remaining ones
       unaffected.  See "The "use locale" pragma" in perllocale for details.

   Perl now supports POSIX 2008 locale currency additions
       On platforms that are able to handle POSIX.1-2008, the hash returned by
       "POSIX::localeconv()" includes the international currency fields added
       by that version of the POSIX standard.  These are "int_n_cs_precedes",
       "int_n_sep_by_space", "int_n_sign_posn", "int_p_cs_precedes",
       "int_p_sep_by_space", and "int_p_sign_posn".

   Better heuristics on older platforms for determining locale UTF-8ness
       On platforms that implement neither the C99 standard nor the POSIX 2001
       standard, determining if the current locale is UTF-8 or not depends on
       heuristics.  These are improved in this release.

   Aliasing via reference
       Variables and subroutines can now be aliased by assigning to a
       reference:

           \$c = \$d;
           \&x = \&y;

       Aliasing can also be accomplished by using a backslash before a
       "foreach" iterator variable; this is perhaps the most useful idiom this
       feature provides:

           foreach \%hash (@array_of_hash_refs) { ... }

       This feature is experimental and must be enabled via
       "use feature 'refaliasing'".  It will warn unless the
       "experimental::refaliasing" warnings category is disabled.

       See "Assigning to References" in perlref

   "prototype" with no arguments
       "prototype()" with no arguments now infers $_.  [perl #123514]
       <https://rt.perl.org/Ticket/Display.html?id=123514>.

   New ":const" subroutine attribute
       The "const" attribute can be applied to an anonymous subroutine.  It
       causes the new sub to be executed immediately whenever one is created
       (i.e. when the "sub" expression is evaluated).  Its value is captured
       and used to create a new constant subroutine that is returned.  This
       feature is experimental.  See "Constant Functions" in perlsub.

   "fileno" now works on directory handles
       When the relevant support is available in the operating system, the
       "fileno" builtin now works on directory handles, yielding the
       underlying file descriptor in the same way as for filehandles. On
       operating systems without such support, "fileno" on a directory handle
       continues to return the undefined value, as before, but also sets $! to
       indicate that the operation is not supported.

       Currently, this uses either a "dd_fd" member in the OS "DIR" structure,
       or a dirfd(3) function as specified by POSIX.1-2008.

   List form of pipe open implemented for Win32
       The list form of pipe:

         open my $fh, "-|", "program", @arguments;

       is now implemented on Win32.  It has the same limitations as "system
       LIST" on Win32, since the Win32 API doesn't accept program arguments as
       a list.

   Assignment to list repetition
       "(...) x ..." can now be used within a list that is assigned to, as
       long as the left-hand side is a valid lvalue.  This allows
       "(undef,undef,$foo) = that_function()" to be written as
       "((undef)x2, $foo) = that_function()".

   Infinity and NaN (not-a-number) handling improved
       Floating point values are able to hold the special values infinity,
       negative infinity, and NaN (not-a-number).  Now we more robustly
       recognize and propagate the value in computations, and on output
       normalize them to the strings "Inf", "-Inf", and "NaN".

       See also the POSIX enhancements.

   Floating point parsing has been improved
       Parsing and printing of floating point values has been improved.

       As a completely new feature, hexadecimal floating point literals (like
       "0x1.23p-4")  are now supported, and they can be output with
       "printf "%a"". See "Scalar value constructors" in perldata for more
       details.

   Packing infinity or not-a-number into a character is now fatal
       Before, when trying to pack infinity or not-a-number into a (signed)
       character, Perl would warn, and assumed you tried to pack 0xFF; if you
       gave it as an argument to "chr", "U+FFFD" was returned.

       But now, all such actions ("pack", "chr", and "print '%c'") result in a
       fatal error.

   Experimental C Backtrace API
       Perl now supports (via a C level API) retrieving the C level backtrace
       (similar to what symbolic debuggers like gdb do).

       The backtrace returns the stack trace of the C call frames, with the
       symbol names (function names), the object names (like "perl"), and if
       it can, also the source code locations (file:line).

       The supported platforms are Linux and OS X (some *BSD might work at
       least partly, but they have not yet been tested).

       The feature needs to be enabled with "Configure -Dusecbacktrace".

       See "C backtrace" in perlhacktips for more information.


Security

   Perl is now compiled with "-fstack-protector-strong" if available
       Perl has been compiled with the anti-stack-smashing option
       "-fstack-protector" since 5.10.1.  Now Perl uses the newer variant
       called "-fstack-protector-strong", if available.

   The Safe module could allow outside packages to be replaced
       Critical bugfix: outside packages could be replaced.  Safe has been
       patched to 2.38 to address this.

   Perl is now always compiled with "-D_FORTIFY_SOURCE=2" if available
       The 'code hardening' option called "_FORTIFY_SOURCE", available in gcc
       4.*, is now always used for compiling Perl, if available.

       Note that this isn't necessarily a huge step since in many platforms
       the step had already been taken several years ago: many Linux
       distributions (like Fedora) have been using this option for Perl, and
       OS X has enforced the same for many years.


Incompatible Changes

   Subroutine signatures moved before attributes
       The experimental sub signatures feature, as introduced in 5.20, parsed
       signatures after attributes. In this release, following feedback from
       users of the experimental feature, the positioning has been moved such
       that signatures occur after the subroutine name (if any) and before the
       attribute list (if any).

   "&" and "\&" prototypes accepts only subs
       The "&" prototype character now accepts only anonymous subs ("sub
       {...}"), things beginning with "\&", or an explicit "undef".  Formerly
       it erroneously also allowed references to arrays, hashes, and lists.
       [perl #4539] <https://rt.perl.org/Ticket/Display.html?id=4539>.  [perl
       #123062] <https://rt.perl.org/Ticket/Display.html?id=123062>.  [perl
       #123062] <https://rt.perl.org/Ticket/Display.html?id=123475>.

       In addition, the "\&" prototype was allowing subroutine calls, whereas
       now it only allows subroutines: &foo is still permitted as an argument,
       while "&foo()" and "foo()" no longer are.  [perl #77860]
       <https://rt.perl.org/Ticket/Display.html?id=77860>.

   "use encoding" is now lexical
       The encoding pragma's effect is now limited to lexical scope.  This
       pragma is deprecated, but in the meantime, it could adversely affect
       unrelated modules that are included in the same program; this change
       fixes that.

   List slices returning empty lists
       List slices now return an empty list only if the original list was
       empty (or if there are no indices).  Formerly, a list slice would
       return an empty list if all indices fell outside the original list; now
       it returns a list of "undef" values in that case.  [perl #114498]
       <https://rt.perl.org/Ticket/Display.html?id=114498>.

   "\N{}" with a sequence of multiple spaces is now a fatal error
       E.g. "\N{TOO  MANY SPACES}" or "\N{TRAILING SPACE }".  This has been
       deprecated since v5.18.

   "use UNIVERSAL '...'" is now a fatal error
       Importing functions from "UNIVERSAL" has been deprecated since v5.12,
       and is now a fatal error.  "use UNIVERSAL" without any arguments is
       still allowed.

   In double-quotish "\cX", X must now be a printable ASCII character
       In prior releases, failure to do this raised a deprecation warning.

   Splitting the tokens "(?" and "(*" in regular expressions is now a fatal
       compilation error.
       These had been deprecated since v5.18.

   "qr/foo/x" now ignores all Unicode pattern white space
       The "/x" regular expression modifier allows the pattern to contain
       white space and comments (both of which are ignored) for improved
       readability.  Until now, not all the white space characters that
       Unicode designates for this purpose were handled.  The additional ones
       now recognized are:

           U+0085 NEXT LINE
           U+200E LEFT-TO-RIGHT MARK
           U+200F RIGHT-TO-LEFT MARK
           U+2028 LINE SEPARATOR
           U+2029 PARAGRAPH SEPARATOR

       The use of these characters with "/x" outside bracketed character
       classes and when not preceded by a backslash has raised a deprecation
       warning since v5.18.  Now they will be ignored.

   Comment lines within "(?[ ])" are now ended only by a "\n"
       "(?[ ])"  is an experimental feature, introduced in v5.18.  It operates
       as if "/x" is always enabled.  But there was a difference: comment
       lines (following a "#" character) were terminated by anything matching
       "\R" which includes all vertical whitespace, such as form feeds.  For
       consistency, this is now changed to match what terminates comment lines
       outside "(?[ ])", namely a "\n" (even if escaped), which is the same as
       what terminates a heredoc string and formats.

   "(?[...])" operators now follow standard Perl precedence
       This experimental feature allows set operations in regular expression
       patterns.  Prior to this, the intersection operator had the same
       precedence as the other binary operators.  Now it has higher
       precedence.  This could lead to different outcomes than existing code
       expects (though the documentation has always noted that this change
       might happen, recommending fully parenthesizing the expressions).  See
       "Extended Bracketed Character Classes" in perlrecharclass.

   Omitting "%" and "@" on hash and array names is no longer permitted
       Really old Perl let you omit the "@" on array names and the "%" on hash
       names in some spots.  This has issued a deprecation warning since Perl
       5.000, and is no longer permitted.

   "$!" text is now in English outside the scope of "use locale"
       Previously, the text, unlike almost everything else, always came out
       based on the current underlying locale of the program.  (Also affected
       on some systems is "$^E".)  For programs that are unprepared to handle
       locale differences, this can cause garbage text to be displayed.  It's
       better to display text that is translatable via some tool than garbage
       text which is much harder to figure out.

   "$!" text will be returned in UTF-8 when appropriate
       The stringification of $! and $^E will have the UTF-8 flag set when the
       text is actually non-ASCII UTF-8.  This will enable programs that are
       set up to be locale-aware to properly output messages in the user's
       native language.  Code that needs to continue the 5.20 and earlier
       behavior can do the stringification within the scopes of both
       "use bytes" and "use locale ":messages"".  Within these two scopes, no
       other Perl operations will be affected by locale; only $! and $^E
       stringification.  The "bytes" pragma causes the UTF-8 flag to not be
       set, just as in previous Perl releases.  This resolves [perl #112208]
       <https://rt.perl.org/Ticket/Display.html?id=112208>.

   Support for "?PATTERN?" without explicit operator has been removed
       The "m?PATTERN?" construct, which allows matching a regex only once,
       previously had an alternative form that was written directly with a
       question mark delimiter, omitting the explicit "m" operator.  This
       usage has produced a deprecation warning since 5.14.0.  It is now a
       syntax error, so that the question mark can be available for use in new
       operators.

   "defined(@array)" and "defined(%hash)" are now fatal errors
       These have been deprecated since v5.6.1 and have raised deprecation
       warnings since v5.16.

   Using a hash or an array as a reference are now fatal errors
       For example, "%foo->{"bar"}" now causes a fatal compilation error.
       These have been deprecated since before v5.8, and have raised
       deprecation warnings since then.

   Changes to the "*" prototype
       The "*" character in a subroutine's prototype used to allow barewords
       to take precedence over most, but not all, subroutine names.  It was
       never consistent and exhibited buggy behavior.

       Now it has been changed, so subroutines always take precedence over
       barewords, which brings it into conformity with similarly prototyped
       built-in functions:

           sub splat(*) { ... }
           sub foo { ... }
           splat(foo); # now always splat(foo())
           splat(bar); # still splat('bar') as before
           close(foo); # close(foo())
           close(bar); # close('bar')


Deprecations

   Setting "${^ENCODING}" to anything but "undef"
       This variable allows Perl scripts to be written in an encoding other
       than ASCII or UTF-8.  However, it affects all modules globally, leading
       to wrong answers and segmentation faults.  New scripts should be
       written in UTF-8; old scripts should be converted to UTF-8, which is
       easily done with the piconv utility.

   Use of non-graphic characters in single-character variable names
       The syntax for single-character variable names is more lenient than for
       longer variable names, allowing the one-character name to be a
       punctuation character or even invisible (a non-graphic).  Perl v5.20
       deprecated the ASCII-range controls as such a name.  Now, all non-
       graphic characters that formerly were allowed are deprecated.  The
       practical effect of this occurs only when not under "use utf8", and
       affects just the C1 controls (code points 0x80 through 0xFF), NO-BREAK
       SPACE, and SOFT HYPHEN.

   Inlining of "sub () { $var }" with observable side-effects
       In many cases Perl makes "sub () { $var }" into an inlinable constant
       subroutine, capturing the value of $var at the time the "sub"
       expression is evaluated.  This can break the closure behavior in those
       cases where $var is subsequently modified, since the subroutine won't
       return the changed value. (Note that this all only applies to anonymous
       subroutines with an empty prototype ("sub ()").)

       This usage is now deprecated in those cases where the variable could be
       modified elsewhere.  Perl detects those cases and emits a deprecation
       warning.  Such code will likely change in the future and stop producing
       a constant.

       If your variable is only modified in the place where it is declared,
       then Perl will continue to make the sub inlinable with no warnings.

           sub make_constant {
               my $var = shift;
               return sub () { $var }; # fine
           }

           sub make_constant_deprecated {
               my $var;
               $var = shift;
               return sub () { $var }; # deprecated
           }

           sub make_constant_deprecated2 {
               my $var = shift;
               log_that_value($var); # could modify $var
               return sub () { $var }; # deprecated
           }

       In the second example above, detecting that $var is assigned to only
       once is too hard to detect.  That it happens in a spot other than the
       "my" declaration is enough for Perl to find it suspicious.

       This deprecation warning happens only for a simple variable for the
       body of the sub.  (A "BEGIN" block or "use" statement inside the sub is
       ignored, because it does not become part of the sub's body.)  For more
       complex cases, such as "sub () { do_something() if 0; $var }" the
       behavior has changed such that inlining does not happen if the variable
       is modifiable elsewhere.  Such cases should be rare.

   Use of multiple "/x" regexp modifiers
       It is now deprecated to say something like any of the following:

           qr/foo/xx;
           /(?xax:foo)/;
           use re qw(/amxx);

       That is, now "x" should only occur once in any string of contiguous
       regular expression pattern modifiers.  We do not believe there are any
       occurrences of this in all of CPAN.  This is in preparation for a
       future Perl release having "/xx" permit white-space for readability in
       bracketed character classes (those enclosed in square brackets:
       "[...]").

   Using a NO-BREAK space in a character alias for "\N{...}" is now deprecated
       This non-graphic character is essentially indistinguishable from a
       regular space, and so should not be allowed.  See "CUSTOM ALIASES" in
       charnames.

   A literal "{" should now be escaped in a pattern
       If you want a literal left curly bracket (also called a left brace) in
       a regular expression pattern, you should now escape it by either
       preceding it with a backslash ("\{") or enclosing it within square
       brackets "[{]", or by using "\Q"; otherwise a deprecation warning will
       be raised.  This was first announced as forthcoming in the v5.16
       release; it will allow future extensions to the language to happen.

   Making all warnings fatal is discouraged
       The documentation for fatal warnings notes that "use warnings FATAL =>
       'all'" is discouraged, and provides stronger language about the risks
       of fatal warnings in general.


Performance Enhancements

       o   If a method or class name is known at compile time, a hash is
           precomputed to speed up run-time method lookup.  Also, compound
           method names like "SUPER::new" are parsed at compile time, to save
           having to parse them at run time.

       o   Array and hash lookups (especially nested ones) that use only
           constants or simple variables as keys, are now considerably faster.
           See "Internal Changes" for more details.

       o   "(...)x1", "("constant")x0" and "($scalar)x0" are now optimised in
           list context.  If the right-hand argument is a constant 1, the
           repetition operator disappears.  If the right-hand argument is a
           constant 0, the whole expression is optimised to the empty list, so
           long as the left-hand argument is a simple scalar or constant.
           (That is, "(foo())x0" is not subject to this optimisation.)

       o   "substr" assignment is now optimised into 4-argument "substr" at
           the end of a subroutine (or as the argument to "return").
           Previously, this optimisation only happened in void context.

       o   In "\L...", "\Q...", etc., the extra "stringify" op is now
           optimised away, making these just as fast as "lcfirst",
           "quotemeta", etc.

       o   Assignment to an empty list is now sometimes faster.  In
           particular, it never calls "FETCH" on tied arguments on the right-
           hand side, whereas it used to sometimes.

       o   There is a performance improvement of up to 20% when "length" is
           applied to a non-magical, non-tied string, and either "use bytes"
           is in scope or the string doesn't use UTF-8 internally.

       o   On most perl builds with 64-bit integers, memory usage for non-
           magical, non-tied scalars containing only a floating point value
           has been reduced by between 8 and 32 bytes, depending on OS.

       o   In "@array = split", the assignment can be optimized away, so that
           "split" writes directly to the array.  This optimisation was
           happening only for package arrays other than @_, and only
           sometimes.  Now this optimisation happens almost all the time.

       o   "join" is now subject to constant folding.  So for example
           "join "-", "a", "b"" is converted at compile-time to "a-b".
           Moreover, "join" with a scalar or constant for the separator and a
           single-item list to join is simplified to a stringification, and
           the separator doesn't even get evaluated.

       o   "qq(@array)" is implemented using two ops: a stringify op and a
           join op.  If the "qq" contains nothing but a single array, the
           stringification is optimized away.

       o   "our $var" and "our($s,@a,%h)" in void context are no longer
           evaluated at run time.  Even a whole sequence of "our $foo;"
           statements will simply be skipped over.  The same applies to
           "state" variables.

       o   Many internal functions have been refactored to improve performance
           and reduce their memory footprints.  [perl #121436]
           <https://rt.perl.org/Ticket/Display.html?id=121436> [perl #121906]
           <https://rt.perl.org/Ticket/Display.html?id=121906> [perl #121969]
           <https://rt.perl.org/Ticket/Display.html?id=121969>

       o   "-T" and "-B" filetests will return sooner when an empty file is
           detected.  [perl #121489]
           <https://rt.perl.org/Ticket/Display.html?id=121489>

       o   Hash lookups where the key is a constant are faster.

       o   Subroutines with an empty prototype and a body containing just
           "undef" are now eligible for inlining.  [perl #122728]
           <https://rt.perl.org/Ticket/Display.html?id=122728>

       o   Subroutines in packages no longer need to be stored in typeglobs:
           declaring a subroutine will now put a simple sub reference directly
           in the stash if possible, saving memory.  The typeglob still
           notionally exists, so accessing it will cause the stash entry to be
           upgraded to a typeglob (i.e. this is just an internal
           implementation detail).  This optimization does not currently apply
           to XSUBs or exported subroutines, and method calls will undo it,
           since they cache things in typeglobs.  [perl #120441]
           <https://rt.perl.org/Ticket/Display.html?id=120441>

       o   The functions "utf8::native_to_unicode()" and
           "utf8::unicode_to_native()" (see utf8) are now optimized out on
           ASCII platforms.  There is now not even a minimal performance hit
           in writing code portable between ASCII and EBCDIC platforms.

       o   Win32 Perl uses 8 KB less of per-process memory than before for
           every perl process, because some data is now memory mapped from
           disk and shared between processes from the same perl binary.


Modules and Pragmata

   Updated Modules and Pragmata
       Many of the libraries distributed with perl have been upgraded since
       v5.20.0.  For a complete list of changes, run:

         corelist --diff 5.20.0 5.22.0

       You can substitute your favorite version in place of 5.20.0, too.

       Some notable changes include:

       o   Archive::Tar has been upgraded to version 2.04.

           Tests can now be run in parallel.

       o   attributes has been upgraded to version 0.27.

           The usage of "memEQs" in the XS has been corrected.  [perl #122701]
           <https://rt.perl.org/Ticket/Display.html?id=122701>

           Avoid reading beyond the end of a buffer. [perl #122629]

       o   B has been upgraded to version 1.58.

           It provides a new "B::safename" function, based on the existing
           "B::GV->SAFENAME", that converts "\cOPEN" to "^OPEN".

           Nulled COPs are now of class "B::COP", rather than "B::OP".

           "B::REGEXP" objects now provide a "qr_anoncv" method for accessing
           the implicit CV associated with "qr//" things containing code
           blocks, and a "compflags" method that returns the pertinent flags
           originating from the "qr//blahblah" op.

           "B::PMOP" now provides a "pmregexp" method returning a "B::REGEXP"
           object.  Two new classes, "B::PADNAME" and "B::PADNAMELIST", have
           been introduced.

           A bug where, after an ithread creation or psuedofork,
           special/immortal SVs in the child ithread/psuedoprocess did not
           have the correct class of "B::SPECIAL", has been fixed.  The "id"
           and "outid" PADLIST methods have been added.

       o   B::Concise has been upgraded to version 0.996.

           Null ops that are part of the execution chain are now given
           sequence numbers.

           Private flags for nulled ops are now dumped with mnemonics as they
           would be for the non-nulled counterparts.

       o   B::Deparse has been upgraded to version 1.35.

           It now deparses "+sub : attr { ... }" correctly at the start of a
           statement.  Without the initial "+", "sub" would be a statement
           label.

           "BEGIN" blocks are now emitted in the right place most of the time,
           but the change unfortunately introduced a regression, in that
           "BEGIN" blocks occurring just before the end of the enclosing block
           may appear below it instead.

           "B::Deparse" no longer puts erroneous "local" here and there, such
           as for "LIST = tr/a//d".  [perl #119815]

           Adjacent "use" statements are no longer accidentally nested if one
           contains a "do" block.  [perl #115066]

           Parenthesised arrays in lists passed to "\" are now correctly
           deparsed with parentheses (e.g., "\(@a, (@b), @c)" now retains the
           parentheses around @b), thus preserving the flattening behavior of
           referenced parenthesised arrays.  Formerly, it only worked for one
           array: "\(@a)".

           "local our" is now deparsed correctly, with the "our" included.

           "for($foo; !$bar; $baz) {...}" was deparsed without the "!" (or
           "not").  This has been fixed.

           Core keywords that conflict with lexical subroutines are now
           deparsed with the "CORE::" prefix.

           "foreach state $x (...) {...}" now deparses correctly with "state"
           and not "my".

           "our @array = split(...)" now deparses correctly with "our" in
           those cases where the assignment is optimized away.

           It now deparses "our(LIST)" and typed lexical ("my Dog $spot")
           correctly.

           Deparse $#_ as that instead of as $#{_}.  [perl #123947]
           <https://rt.perl.org/Ticket/Display.html?id=123947>

           BEGIN blocks at the end of the enclosing scope are now deparsed in
           the right place.  [perl #77452]

           BEGIN blocks were sometimes deparsed as __ANON__, but are now
           always called BEGIN.

           Lexical subroutines are now fully deparsed.  [perl #116553]

           "Anything =~ y///r" with "/r" no longer omits the left-hand
           operand.

           The op trees that make up regexp code blocks are now deparsed for
           real.  Formerly, the original string that made up the regular
           expression was used.  That caused problems with
           "qr/(?{<<heredoc})/" and multiline code blocks, which were deparsed
           incorrectly.  [perl #123217] [perl #115256]

           $; at the end of a statement no longer loses its semicolon.  [perl
           #123357]

           Some cases of subroutine declarations stored in the stash in
           shorthand form were being omitted.

           Non-ASCII characters are now consistently escaped in strings,
           instead of some of the time.  (There are still outstanding problems
           with regular expressions and identifiers that have not been fixed.)

           When prototype sub calls are deparsed with "&" (e.g., under the -P
           option), "scalar" is now added where appropriate, to force the
           scalar context implied by the prototype.

           "require(foo())", "do(foo())", "goto(foo())" and similar constructs
           with loop controls are now deparsed correctly.  The outer
           parentheses are not optional.

           Whitespace is no longer escaped in regular expressions, because it
           was getting erroneously escaped within "(?x:...)" sections.

           "sub foo { foo() }" is now deparsed with those mandatory
           parentheses.

           "/@array/" is now deparsed as a regular expression, and not just
           @array.

           "/@{-}/", "/@{+}/" and $#{1} are now deparsed with the braces,
           which are mandatory in these cases.

           In deparsing feature bundles, "B::Deparse" was emitting "no
           feature;" first instead of "no feature ':all';".  This has been
           fixed.

           "chdir FH" is now deparsed without quotation marks.

           "\my @a" is now deparsed without parentheses.  (Parenthese would
           flatten the array.)

           "system" and "exec" followed by a block are now deparsed correctly.
           Formerly there was an erroneous "do" before the block.

           "use constant QR => qr/.../flags" followed by """ =~ QR" is no
           longer without the flags.

           Deparsing "BEGIN { undef &foo }" with the -w switch enabled started
           to emit 'uninitialized' warnings in Perl 5.14.  This has been
           fixed.

           Deparsing calls to subs with a "(;+)" prototype resulted in an
           infinite loop.  The "(;$") "(_)" and "(;_)" prototypes were given
           the wrong precedence, causing "foo($a<$b)" to be deparsed without
           the parentheses.

           Deparse now provides a defined state sub in inner subs.

       o   B::Op_private has been added.

           B::Op_private provides detailed information about the flags used in
           the "op_private" field of perl opcodes.

       o   bigint, bignum, bigrat have been upgraded to version 0.39.

           Document in CAVEATS that using strings as numbers won't always
           invoke the big number overloading, and how to invoke it.
           [rt.perl.org #123064]

       o   Carp has been upgraded to version 1.36.

           "Carp::Heavy" now ignores version mismatches with Carp if Carp is
           newer than 1.12, since "Carp::Heavy"'s guts were merged into Carp
           at that point.  [perl #121574]
           <https://rt.perl.org/Ticket/Display.html?id=121574>

           Carp now handles non-ASCII platforms better.

           Off-by-one error fix for Perl < 5.14.

       o   constant has been upgraded to version 1.33.

           It now accepts fully-qualified constant names, allowing constants
           to be defined in packages other than the caller.

       o   CPAN has been upgraded to version 2.11.

           Add support for "Cwd::getdcwd()" and introduce workaround for a
           misbehavior seen on Strawberry Perl 5.20.1.

           Fix "chdir()" after building dependencies bug.

           Introduce experimental support for plugins/hooks.

           Integrate the "App::Cpan" sources.

           Do not check recursion on optional dependencies.

           Sanity check META.yml to contain a hash.  [cpan #95271]
           <https://rt.cpan.org/Ticket/Display.html?id=95271>

       o   CPAN::Meta::Requirements has been upgraded to version 2.132.

           Works around limitations in "version::vpp" detecting v-string magic
           and adds support for forthcoming ExtUtils::MakeMaker bootstrap
           version.pm for Perls older than 5.10.0.

       o   Data::Dumper has been upgraded to version 2.158.

           Fixes CVE-2014-4330 by adding a configuration variable/option to
           limit recursion when dumping deep data structures.

           Changes to resolve Coverity issues.  XS dumps incorrectly stored
           the name of code references stored in a GLOB.  [perl #122070]
           <https://rt.perl.org/Ticket/Display.html?id=122070>

       o   DynaLoader has been upgraded to version 1.32.

           Remove "dl_nonlazy" global if unused in Dynaloader. [perl #122926]

       o   Encode has been upgraded to version 2.72.

           "piconv" now has better error handling when the encoding name is
           nonexistent, and a build breakage when upgrading Encode in
           perl-5.8.2 and earlier has been fixed.

           Building in C++ mode on Windows now works.

       o   Errno has been upgraded to version 1.23.

           Add "-P" to the preprocessor command-line on GCC 5.  GCC added
           extra line directives, breaking parsing of error code definitions.
           [rt.perl.org #123784]

       o   experimental has been upgraded to version 0.013.

           Hardcodes features for Perls older than 5.15.7.

       o   ExtUtils::CBuilder has been upgraded to version 0.280221.

           Fixes a regression on Android.  [perl #122675]
           <https://rt.perl.org/Ticket/Display.html?id=122675>

       o   ExtUtils::Manifest has been upgraded to version 1.70.

           Fixes a bug with "maniread()"'s handling of quoted filenames and
           improves "manifind()" to follow symlinks.  [perl #122415]
           <https://rt.perl.org/Ticket/Display.html?id=122415>

       o   ExtUtils::ParseXS has been upgraded to version 3.28.

           Only declare "file" unused if we actually define it.  Improve
           generated "RETVAL" code generation to avoid repeated references to
           ST(0).  [perl #123278] Broaden and document the "/OBJ$/" to
           "/REF$/" typemap optimization for the "DESTROY" method.  [perl
           #123418]

       o   Fcntl has been upgraded to version 1.13.

           Add support for the Linux pipe buffer size "fcntl()" commands.

       o   File::Find has been upgraded to version 1.29.

           "find()" and "finddepth()" will now warn if passed inappropriate or
           misspelled options.

       o   File::Glob has been upgraded to version 1.24.

           Avoid "SvIV()" expanding to call "get_sv()" three times in a few
           places. [perl #123606]

       o   HTTP::Tiny has been upgraded to version 0.054.

           "keep_alive" is now fork-safe and thread-safe.

       o   IO has been upgraded to version 1.35.

           The XS implementation has been fixed for the sake of older Perls.

       o   IO::Socket has been upgraded to version 1.38.

           Document the limitations of the "connected()" method.  [perl
           #123096]

       o   IO::Socket::IP has been upgraded to version 0.37.

           A better fix for subclassing "connect()".  [cpan #95983]
           <https://rt.cpan.org/Ticket/Display.html?id=95983> [cpan #97050]
           <https://rt.cpan.org/Ticket/Display.html?id=97050>

           Implements Timeout for "connect()".  [cpan #92075]
           <https://rt.cpan.org/Ticket/Display.html?id=92075>

       o   The libnet collection of modules has been upgraded to version 3.05.

           Support for IPv6 and SSL to "Net::FTP", "Net::NNTP", "Net::POP3"
           and "Net::SMTP".  Improvements in "Net::SMTP" authentication.

       o   Locale::Codes has been upgraded to version 3.34.

           Fixed a bug in the scripts used to extract data from spreadsheets
           that prevented the SHP currency code from being found.  [cpan
           #94229] <https://rt.cpan.org/Ticket/Display.html?id=94229>

           New codes have been added.

       o   Math::BigInt has been upgraded to version 1.9997.

           Synchronize POD changes from the CPAN release.
           "Math::BigFloat->blog(x)" would sometimes return "blog(2*x)" when
           the accuracy was greater than 70 digits.  The result of
           "Math::BigFloat->bdiv()" in list context now satisfies "x =
           quotient * divisor + remainder".

           Correct handling of subclasses.  [cpan #96254]
           <https://rt.cpan.org/Ticket/Display.html?id=96254> [cpan #96329]
           <https://rt.cpan.org/Ticket/Display.html?id=96329>

       o   Module::Metadata has been upgraded to version 1.000026.

           Support installations on older perls with an ExtUtils::MakeMaker
           earlier than 6.63_03

       o   overload has been upgraded to version 1.26.

           A redundant "ref $sub" check has been removed.

       o   The PathTools module collection has been upgraded to version 3.56.

           A warning from the gcc compiler is now avoided when building the
           XS.

           Don't turn leading "//" into "/" on Cygwin. [perl #122635]

       o   perl5db.pl has been upgraded to version 1.49.

           The debugger would cause an assertion failure.  [perl #124127]
           <https://rt.perl.org/Ticket/Display.html?id=124127>

           "fork()" in the debugger under "tmux" will now create a new window
           for the forked process. [perl #121333]
           <https://rt.perl.org/Ticket/Display.html?id=121333>

           The debugger now saves the current working directory on startup and
           restores it when you restart your program with "R" or "rerun".
           [perl #121509] <https://rt.perl.org/Ticket/Display.html?id=121509>

       o   PerlIO::scalar has been upgraded to version 0.22.

           Reading from a position well past the end of the scalar now
           correctly returns end of file.  [perl #123443]

           Seeking to a negative position still fails, but no longer leaves
           the file position set to a negation location.

           "eof()" on a "PerlIO::scalar" handle now properly returns true when
           the file position is past the 2GB mark on 32-bit systems.

           Attempting to write at file positions impossible for the platform
           now fail early rather than wrapping at 4GB.

       o   Pod::Perldoc has been upgraded to version 3.25.

           Filehandles opened for reading or writing now have
           ":encoding(UTF-8)" set.  [cpan #98019]
           <https://rt.cpan.org/Ticket/Display.html?id=98019>

       o   POSIX has been upgraded to version 1.53.

           The C99 math functions and constants (for example "acosh", "isinf",
           "isnan", "round", "trunc"; "M_E", "M_SQRT2", "M_PI") have been
           added.

           "POSIX::tmpnam()" now produces a deprecation warning.  [perl
           #122005]

       o   Safe has been upgraded to version 2.39.

           "reval" was not propagating void context properly.

       o   Scalar-List-Utils has been upgraded to version 1.41.

           A new module, Sub::Util, has been added, containing functions
           related to CODE refs, including "subname" (inspired by
           "Sub::Identity") and "set_subname" (copied and renamed from
           "Sub::Name").  The use of "GetMagic" in "List::Util::reduce()" has
           also been fixed.  [cpan #63211]
           <https://rt.cpan.org/Ticket/Display.html?id=63211>

       o   SDBM_File has been upgraded to version 1.13.

           Simplified the build process.  [perl #123413]

       o   Time::Piece has been upgraded to version 1.29.

           When pretty printing negative "Time::Seconds", the "minus" is no
           longer lost.

       o   Unicode::Collate has been upgraded to version 1.12.

           Version 0.67's improved discontiguous contractions is invalidated
           by default and is supported as a parameter "long_contraction".

       o   Unicode::Normalize has been upgraded to version 1.18.

           The XSUB implementation has been removed in favor of pure Perl.

       o   Unicode::UCD has been upgraded to version 0.61.

           A new function property_values() has been added to return a given
           property's possible values.

           A new function charprop() has been added to return the value of a
           given property for a given code point.

           A new function charprops_all() has been added to return the values
           of all Unicode properties for a given code point.

           A bug has been fixed so that propaliases() returns the correct
           short and long names for the Perl extensions where it was
           incorrect.

           A bug has been fixed so that prop_value_aliases() returns "undef"
           instead of a wrong result for properties that are Perl extensions.

           This module now works on EBCDIC platforms.

       o   utf8 has been upgraded to version 1.17

           A mismatch between the documentation and the code in
           "utf8::downgrade()" was fixed in favor of the documentation. The
           optional second argument is now correctly treated as a perl boolean
           (true/false semantics) and not as an integer.

       o   version has been upgraded to version 0.9909.

           Numerous changes.  See the Changes file in the CPAN distribution
           for details.

       o   Win32 has been upgraded to version 0.51.

           "GetOSName()" now supports Windows 8.1, and building in C++ mode
           now works.

       o   Win32API::File has been upgraded to version 0.1202

           Building in C++ mode now works.

       o   XSLoader has been upgraded to version 0.20.

           Allow XSLoader to load modules from a different namespace.  [perl
           #122455]

   Removed Modules and Pragmata
       The following modules (and associated modules) have been removed from
       the core perl distribution:

       o   CGI

       o   Module::Build


Documentation

   New Documentation
       perlunicook

       This document, by Tom Christiansen, provides examples of handling
       Unicode in Perl.

   Changes to Existing Documentation
       perlaix

       o   A note on long doubles has been added.

       perlapi

       o   Note that "SvSetSV" doesn't do set magic.

       o   "sv_usepvn_flags" - fix documentation to mention the use of "Newx"
           instead of "malloc".

           [perl #121869] <https://rt.perl.org/Ticket/Display.html?id=121869>

       o   Clarify where "NUL" may be embedded or is required to terminate a
           string.

       o   Some documentation that was previously missing due to formatting
           errors is now included.

       o   Entries are now organized into groups rather than by the file where
           they are found.

       o   Alphabetical sorting of entries is now done consistently
           (automatically by the POD generator) to make entries easier to find
           when scanning.

       perldata

       o   The syntax of single-character variable names has been brought up-
           to-date and more fully explained.

       o   Hexadecimal floating point numbers are described, as are infinity
           and NaN.

       perlebcdic

       o   This document has been significantly updated in the light of recent
           improvements to EBCDIC support.

       perlfilter

       o   Added a LIMITATIONS section.

       perlfunc

       o   Mention that "study()" is currently a no-op.

       o   Calling "delete" or "exists" on array values is now described as
           "strongly discouraged" rather than "deprecated".

       o   Improve documentation of "our".

       o   "-l" now notes that it will return false if symlinks aren't
           supported by the file system.  [perl #121523]
           <https://rt.perl.org/Ticket/Display.html?id=121523>

       o   Note that "exec LIST" and "system LIST" may fall back to the shell
           on Win32. Only the indirect-object syntax "exec PROGRAM LIST" and
           "system PROGRAM LIST" will reliably avoid using the shell.

           This has also been noted in perlport.

           [perl #122046] <https://rt.perl.org/Ticket/Display.html?id=122046>

       perlguts

       o   The OOK example has been updated to account for COW changes and a
           change in the storage of the offset.

       o   Details on C level symbols and libperl.t added.

       o   Information on Unicode handling has been added

       o   Information on EBCDIC handling has been added

       perlhack

       o   A note has been added about running on platforms with non-ASCII
           character sets

       o   A note has been added about performance testing

       perlhacktips

       o   Documentation has been added illustrating the perils of assuming
           that there is no change to the contents of static memory pointed to
           by the return values of Perl's wrappers for C library functions.

       o   Replacements for "tmpfile", "atoi", "strtol", and "strtoul" are now
           recommended.

       o   Updated documentation for the "test.valgrind" "make" target.  [perl
           #121431] <https://rt.perl.org/Ticket/Display.html?id=121431>

       o   Information is given about writing test files portably to non-ASCII
           platforms.

       o   A note has been added about how to get a C language stack
           backtrace.

       perlhpux

       o   Note that the message "Redeclaration of "sendpath" with a different
           storage class specifier" is harmless.

       perllocale

       o   Updated for the enhancements in v5.22, along with some
           clarifications.

       perlmodstyle

       o   Instead of pointing to the module list, we are now pointing to
           PrePAN <http://prepan.org/>.

       perlop

       o   Updated for the enhancements in v5.22, along with some
           clarifications.

       perlpodspec

       o   The specification of the pod language is changing so that the
           default encoding of pods that aren't in UTF-8 (unless otherwise
           indicated) is CP1252 instead of ISO 8859-1 (Latin1).

       perlpolicy

       o   We now have a code of conduct for the p5p mailing list, as
           documented in "STANDARDS OF CONDUCT" in perlpolicy.

       o   The conditions for marking an experimental feature as non-
           experimental are now set out.

       o   Clarification has been made as to what sorts of changes are
           permissible in maintenance releases.

       perlport

       o   Out-of-date VMS-specific information has been fixed and/or
           simplified.

       o   Notes about EBCDIC have been added.

       perlre

       o   The description of the "/x" modifier has been clarified to note
           that comments cannot be continued onto the next line by escaping
           them; and there is now a list of all the characters that are
           considered whitespace by this modifier.

       o   The new "/n" modifier is described.

       o   A note has been added on how to make bracketed character class
           ranges portable to non-ASCII machines.

       perlrebackslash

       o   Added documentation of "\b{sb}", "\b{wb}", "\b{gcb}", and "\b{g}".

       perlrecharclass

       o   Clarifications have been added to "Character Ranges" in
           perlrecharclass to the effect "[A-Z]", "[a-z]", "[0-9]" and any
           subranges thereof in regular expression bracketed character classes
           are guaranteed to match exactly what a naive English speaker would
           expect them to match, even on platforms (such as EBCDIC) where perl
           has to do extra work to accomplish this.

       o   The documentation of Bracketed Character Classes has been expanded
           to cover the improvements in "qr/[\N{named sequence}]/" (see under
           "Selected Bug Fixes").

       perlref

       o   A new section has been added Assigning to References

       perlsec

       o   Comments added on algorithmic complexity and tied hashes.

       perlsyn

       o   An ambiguity in the documentation of the "..." statement has been
           corrected.  [perl #122661]
           <https://rt.perl.org/Ticket/Display.html?id=122661>

       o   The empty conditional in "for" and "while" is now documented in
           perlsyn.

       perlunicode

       o   This has had extensive revisions to bring it up-to-date with
           current Unicode support and to make it more readable.  Notable is
           that Unicode 7.0 changed what it should do with non-characters.
           Perl retains the old way of handling for reasons of backward
           compatibility.  See "Noncharacter code points" in perlunicode.

       perluniintro

       o   Advice for how to make sure your strings and regular expression
           patterns are interpreted as Unicode has been updated.

       perlvar

       o   $] is no longer listed as being deprecated.  Instead, discussion
           has been added on the advantages and disadvantages of using it
           versus $^V.  $OLD_PERL_VERSION was re-added to the documentation as
           the long form of $].

       o   "${^ENCODING}" is now marked as deprecated.

       o   The entry for "%^H" has been clarified to indicate it can only
           handle simple values.

       perlvms

       o   Out-of-date and/or incorrect material has been removed.

       o   Updated documentation on environment and shell interaction in VMS.

       perlxs

       o   Added a discussion of locale issues in XS code.


Diagnostics

       The following additions or changes have been made to diagnostic output,
       including warnings and fatal error messages.  For the complete list of
       diagnostic messages, see perldiag.

   New Diagnostics
       New Errors

       o   Bad symbol for scalar

           (P) An internal request asked to add a scalar entry to something
           that wasn't a symbol table entry.

       o   Can't use a hash as a reference

           (F) You tried to use a hash as a reference, as in "%foo->{"bar"}"
           or "%$ref->{"hello"}".  Versions of perl <= 5.6.1 used to allow
           this syntax, but shouldn't have.

       o   Can't use an array as a reference

           (F) You tried to use an array as a reference, as in "@foo->[23]" or
           "@$ref->[99]".  Versions of perl <= 5.6.1 used to allow this
           syntax, but shouldn't have.

       o   Can't use 'defined(@array)' (Maybe you should just omit the
           defined()?)

           (F) "defined()" is not useful on arrays because it checks for an
           undefined scalar value.  If you want to see if the array is empty,
           just use "if (@array) { # not empty }" for example.

       o   Can't use 'defined(%hash)' (Maybe you should just omit the
           defined()?)

           (F) "defined()" is not usually right on hashes.

           Although "defined %hash" is false on a plain not-yet-used hash, it
           becomes true in several non-obvious circumstances, including
           iterators, weak references, stash names, even remaining true after
           "undef %hash".  These things make "defined %hash" fairly useless in
           practice, so it now generates a fatal error.

           If a check for non-empty is what you wanted then just put it in
           boolean context (see "Scalar values" in perldata):

               if (%hash) {
                  # not empty
               }

           If you had "defined %Foo::Bar::QUUX" to check whether such a
           package variable exists then that's never really been reliable, and
           isn't a good way to enquire about the features of a package, or
           whether it's loaded, etc.

       o   Cannot chr %f

           (F) You passed an invalid number (like an infinity or not-a-number)
           to "chr".

       o   Cannot compress %f in pack

           (F) You tried converting an infinity or not-a-number to an unsigned
           character, which makes no sense.

       o   Cannot pack %f with '%c'

           (F) You tried converting an infinity or not-a-number to a
           character, which makes no sense.

       o   Cannot print %f with '%c'

           (F) You tried printing an infinity or not-a-number as a character
           (%c), which makes no sense.  Maybe you meant '%s', or just
           stringifying it?

       o   charnames alias definitions may not contain a sequence of multiple
           spaces

           (F) You defined a character name which had multiple space
           characters in a row.  Change them to single spaces.  Usually these
           names are defined in the ":alias" import argument to "use
           charnames", but they could be defined by a translator installed
           into $^H{charnames}.  See "CUSTOM ALIASES" in charnames.

       o   charnames alias definitions may not contain trailing white-space

           (F) You defined a character name which ended in a space character.
           Remove the trailing space(s).  Usually these names are defined in
           the ":alias" import argument to "use charnames", but they could be
           defined by a translator installed into $^H{charnames}.  See "CUSTOM
           ALIASES" in charnames.

       o   :const is not permitted on named subroutines

           (F) The "const" attribute causes an anonymous subroutine to be run
           and its value captured at the time that it is cloned.  Named
           subroutines are not cloned like this, so the attribute does not
           make sense on them.

       o   Hexadecimal float: internal error

           (F) Something went horribly bad in hexadecimal float handling.

       o   Hexadecimal float: unsupported long double format

           (F) You have configured Perl to use long doubles but the internals
           of the long double format are unknown, therefore the hexadecimal
           float output is impossible.

       o   Illegal suidscript

           (F) The script run under suidperl was somehow illegal.

       o   In '(?...)', the '(' and '?' must be adjacent in regex; marked by
           <-- HERE in m/%s/

           (F) The two-character sequence "(?" in this context in a regular
           expression pattern should be an indivisible token, with nothing
           intervening between the "(" and the "?", but you separated them.

       o   In '(*VERB...)', the '(' and '*' must be adjacent in regex; marked
           by <-- HERE in m/%s/

           (F) The two-character sequence "(*" in this context in a regular
           expression pattern should be an indivisible token, with nothing
           intervening between the "(" and the "*", but you separated them.

       o   Invalid quantifier in {,} in regex; marked by <-- HERE in m/%s/

           (F) The pattern looks like a {min,max} quantifier, but the min or
           max could not be parsed as a valid number: either it has leading
           zeroes, or it represents too big a number to cope with.  The
           <-- HERE shows where in the regular expression the problem was
           discovered.  See perlre.

       o   '%s' is an unknown bound type in regex

           (F) You used "\b{...}" or "\B{...}" and the "..." is not known to
           Perl.  The current valid ones are given in "\b{}, \b, \B{}, \B" in
           perlrebackslash.

       o   Missing or undefined argument to require

           (F) You tried to call "require" with no argument or with an
           undefined value as an argument.  "require" expects either a package
           name or a file-specification as an argument.  See "require" in
           perlfunc.

           Formerly, "require" with no argument or "undef" warned about a Null
           filename.

       New Warnings

       o   \C is deprecated in regex

           (D deprecated) The "/\C/" character class was deprecated in v5.20,
           and now emits a warning. It is intended that it will become an
           error in v5.24.  This character class matches a single byte even if
           it appears within a multi-byte character, breaks encapsulation, and
           can corrupt UTF-8 strings.

       o   "%s" is more clearly written simply as "%s" in regex; marked by <--
           HERE in m/%s/

           (W regexp) (only under "use re 'strict'" or within "(?[...])")

           You specified a character that has the given plainer way of writing
           it, and which is also portable to platforms running with different
           character sets.

       o   Argument "%s" treated as 0 in increment (++)

           (W numeric) The indicated string was fed as an argument to the "++"
           operator which expects either a number or a string matching
           "/^[a-zA-Z]*[0-9]*\z/".  See "Auto-increment and Auto-decrement" in
           perlop for details.

       o   Both or neither range ends should be Unicode in regex; marked by
           <-- HERE in m/%s/

           (W regexp) (only under "use re 'strict'" or within "(?[...])")

           In a bracketed character class in a regular expression pattern, you
           had a range which has exactly one end of it specified using "\N{}",
           and the other end is specified using a non-portable mechanism.
           Perl treats the range as a Unicode range, that is, all the
           characters in it are considered to be the Unicode characters, and
           which may be different code points on some platforms Perl runs on.
           For example, "[\N{U+06}-\x08]" is treated as if you had instead
           said "[\N{U+06}-\N{U+08}]", that is it matches the characters whose
           code points in Unicode are 6, 7, and 8.  But that "\x08" might
           indicate that you meant something different, so the warning gets
           raised.

       o   Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".

           (W locale) You are 1) running under ""use locale""; 2) the current
           locale is not a UTF-8 one; 3) you tried to do the designated case-
           change operation on the specified Unicode character; and 4) the
           result of this operation would mix Unicode and locale rules, which
           likely conflict.

           The warnings category "locale" is new.

       o   :const is experimental

           (S experimental::const_attr) The "const" attribute is experimental.
           If you want to use the feature, disable the warning with "no
           warnings 'experimental::const_attr'", but know that in doing so you
           are taking the risk that your code may break in a future Perl
           version.

       o   gmtime(%f) failed

           (W overflow) You called "gmtime" with a number that it could not
           handle: too large, too small, or NaN.  The returned value is
           "undef".

       o   Hexadecimal float: exponent overflow

           (W overflow) The hexadecimal floating point has larger exponent
           than the floating point supports.

       o   Hexadecimal float: exponent underflow

           (W overflow) The hexadecimal floating point has smaller exponent
           than the floating point supports.

       o   Hexadecimal float: mantissa overflow

           (W overflow) The hexadecimal floating point literal had more bits
           in the mantissa (the part between the "0x" and the exponent, also
           known as the fraction or the significand) than the floating point
           supports.

       o   Hexadecimal float: precision loss

           (W overflow) The hexadecimal floating point had internally more
           digits than could be output.  This can be caused by unsupported
           long double formats, or by 64-bit integers not being available
           (needed to retrieve the digits under some configurations).

       o   Locale '%s' may not work well.%s

           (W locale) You are using the named locale, which is a non-UTF-8
           one, and which perl has determined is not fully compatible with
           what it can handle.  The second %s gives a reason.

           The warnings category "locale" is new.

       o   localtime(%f) failed

           (W overflow) You called "localtime" with a number that it could not
           handle: too large, too small, or NaN.  The returned value is
           "undef".

       o   Negative repeat count does nothing

           (W numeric) You tried to execute the "x" repetition operator fewer
           than 0 times, which doesn't make sense.

       o   NO-BREAK SPACE in a charnames alias definition is deprecated

           (D deprecated) You defined a character name which contained a no-
           break space character.  Change it to a regular space.  Usually
           these names are defined in the ":alias" import argument to "use
           charnames", but they could be defined by a translator installed
           into $^H{charnames}.  See "CUSTOM ALIASES" in charnames.

       o   Non-finite repeat count does nothing

           (W numeric) You tried to execute the "x" repetition operator "Inf"
           (or "-Inf") or NaN times, which doesn't make sense.

       o   PerlIO layer ':win32' is experimental

           (S experimental::win32_perlio) The ":win32" PerlIO layer is
           experimental.  If you want to take the risk of using this layer,
           simply disable this warning:

               no warnings "experimental::win32_perlio";

       o   Ranges of ASCII printables should be some subset of "0-9", "A-Z",
           or "a-z" in regex; marked by <-- HERE in m/%s/

           (W regexp) (only under "use re 'strict'" or within "(?[...])")

           Stricter rules help to find typos and other errors.  Perhaps you
           didn't even intend a range here, if the "-" was meant to be some
           other character, or should have been escaped (like "\-").  If you
           did intend a range, the one that was used is not portable between
           ASCII and EBCDIC platforms, and doesn't have an obvious meaning to
           a casual reader.

            [3-7]    # OK; Obvious and portable
            [d-g]    # OK; Obvious and portable
            [A-Y]    # OK; Obvious and portable
            [A-z]    # WRONG; Not portable; not clear what is meant
            [a-Z]    # WRONG; Not portable; not clear what is meant
            [%-.]    # WRONG; Not portable; not clear what is meant
            [\x41-Z] # WRONG; Not portable; not obvious to non-geek

           (You can force portability by specifying a Unicode range, which
           means that the endpoints are specified by "\N{...}", but the
           meaning may still not be obvious.)  The stricter rules require that
           ranges that start or stop with an ASCII character that is not a
           control have all their endpoints be a literal character, and not
           some escape sequence (like "\x41"), and the ranges must be all
           digits, or all uppercase letters, or all lowercase letters.

       o   Ranges of digits should be from the same group in regex; marked by
           <-- HERE in m/%s/

           (W regexp) (only under "use re 'strict'" or within "(?[...])")

           Stricter rules help to find typos and other errors.  You included a
           range, and at least one of the end points is a decimal digit.
           Under the stricter rules, when this happens, both end points should
           be digits in the same group of 10 consecutive digits.

       o   Redundant argument in %s

           (W redundant) You called a function with more arguments than were
           needed, as indicated by information within other arguments you
           supplied (e.g. a printf format). Currently only emitted when a
           printf-type format required fewer arguments than were supplied, but
           might be used in the future for e.g. "pack" in perlfunc.

           The warnings category "redundant" is new. See also [perl #121025]
           <https://rt.perl.org/Ticket/Display.html?id=121025>.

       o   Replacement list is longer than search list

           This is not a new diagnostic, but in earlier releases was
           accidentally not displayed if the transliteration contained wide
           characters.  This is now fixed, so that you may see this diagnostic
           in places where you previously didn't (but should have).

       o   Use of \b{} for non-UTF-8 locale is wrong.  Assuming a UTF-8 locale

           (W locale) You are matching a regular expression using locale
           rules, and a Unicode boundary is being matched, but the locale is
           not a Unicode one.  This doesn't make sense.  Perl will continue,
           assuming a Unicode (UTF-8) locale, but the results could well be
           wrong except if the locale happens to be ISO-8859-1 (Latin1) where
           this message is spurious and can be ignored.

           The warnings category "locale" is new.

       o   Using /u for '%s' instead of /%s in regex; marked by <-- HERE in
           m/%s/

           (W regexp) You used a Unicode boundary ("\b{...}" or "\B{...}") in
           a portion of a regular expression where the character set modifiers
           "/a" or "/aa" are in effect.  These two modifiers indicate an ASCII
           interpretation, and this doesn't make sense for a Unicode
           definition.  The generated regular expression will compile so that
           the boundary uses all of Unicode.  No other portion of the regular
           expression is affected.

       o   The bitwise feature is experimental

           (S experimental::bitwise) This warning is emitted if you use
           bitwise operators ("& | ^ ~ &. |. ^. ~.") with the "bitwise"
           feature enabled.  Simply suppress the warning if you want to use
           the feature, but know that in doing so you are taking the risk of
           using an experimental feature which may change or be removed in a
           future Perl version:

               no warnings "experimental::bitwise";
               use feature "bitwise";
               $x |.= $y;

       o   Unescaped left brace in regex is deprecated, passed through in
           regex; marked by <-- HERE in m/%s/

           (D deprecated, regexp) You used a literal "{" character in a
           regular expression pattern. You should change to use "\{" instead,
           because a future version of Perl (tentatively v5.26) will consider
           this to be a syntax error.  If the pattern delimiters are also
           braces, any matching right brace ("}") should also be escaped to
           avoid confusing the parser, for example,

               qr{abc\{def\}ghi}

       o   Use of literal non-graphic characters in variable names is
           deprecated

           (D deprecated) Using literal non-graphic (including control)
           characters in the source to refer to the ^FOO variables, like $^X
           and "${^GLOBAL_PHASE}" is now deprecated.

       o   Useless use of attribute "const"

           (W misc) The "const" attribute has no effect except on anonymous
           closure prototypes.  You applied it to a subroutine via
           attributes.pm.  This is only useful inside an attribute handler for
           an anonymous subroutine.

       o   Useless use of /d modifier in transliteration operator

           This is not a new diagnostic, but in earlier releases was
           accidentally not displayed if the transliteration contained wide
           characters.  This is now fixed, so that you may see this diagnostic
           in places where you previously didn't (but should have).

       o   "use re 'strict'" is experimental

           (S experimental::re_strict) The things that are different when a
           regular expression pattern is compiled under 'strict' are subject
           to change in future Perl releases in incompatible ways; there are
           also proposals to change how to enable strict checking instead of
           using this subpragma.  This means that a pattern that compiles
           today may not in a future Perl release.  This warning is to alert
           you to that risk.

       o   Warning: unable to close filehandle properly: %s

           Warning: unable to close filehandle %s properly: %s

           (S io) Previously, perl silently ignored any errors when doing an
           implicit close of a filehandle, i.e. where the reference count of
           the filehandle reached zero and the user's code hadn't already
           called "close()"; e.g.

               {
                   open my $fh, '>', $file  or die "open: '$file': $!\n";
                   print $fh, $data  or die;
               } # implicit close here

           In a situation such as disk full, due to buffering, the error may
           only be detected during the final close, so not checking the result
           of the close is dangerous.

           So perl now warns in such situations.

       o   Wide character (U+%X) in %s

           (W locale) While in a single-byte locale (i.e., a non-UTF-8 one), a
           multi-byte character was encountered.   Perl considers this
           character to be the specified Unicode code point.  Combining
           non-UTF-8 locales and Unicode is dangerous.  Almost certainly some
           characters will have two different representations.  For example,
           in the ISO 8859-7 (Greek) locale, the code point 0xC3 represents a
           Capital Gamma.  But so also does 0x393.  This will make string
           comparisons unreliable.

           You likely need to figure out how this multi-byte character got
           mixed up with your single-byte locale (or perhaps you thought you
           had a UTF-8 locale, but Perl disagrees).

           The warnings category "locale" is new.

   Changes to Existing Diagnostics
       o   <> should be quotes

           This warning has been changed to <> at require-statement should be
           quotes to make the issue more identifiable.

       o   Argument "%s" isn't numeric%s

           The perldiag entry for this warning has added this clarifying note:

            Note that for the Inf and NaN (infinity and not-a-number) the
            definition of "numeric" is somewhat unusual: the strings themselves
            (like "Inf") are considered numeric, and anything following them is
            considered non-numeric.

       o   Global symbol "%s" requires explicit package name

           This message has had '(did you forget to declare "my %s"?)'
           appended to it, to make it more helpful to new Perl programmers.
           [perl #121638] <https://rt.perl.org/Ticket/Display.html?id=121638>

       o   '"my" variable &foo::bar can't be in a package' has been reworded
           to say 'subroutine' instead of 'variable'.

       o   \N{} in character class restricted to one character in regex;
           marked by <-- HERE in m/%s/

           This message has had character class changed to inverted character
           class or as a range end-point is to reflect improvements in
           "qr/[\N{named sequence}]/" (see under "Selected Bug Fixes").

       o   panic: frexp

           This message has had ': %f' appended to it, to show what the
           offending floating point number is.

       o   Possible precedence problem on bitwise %c operator reworded as
           Possible precedence problem on bitwise %s operator.

       o   Unsuccessful %s on filename containing newline

           This warning is now only produced when the newline is at the end of
           the filename.

       o   "Variable %s will not stay shared" has been changed to say
           "Subroutine" when it is actually a lexical sub that will not stay
           shared.

       o   Variable length lookbehind not implemented in regex m/%s/

           The perldiag entry for this warning has had information about
           Unicode behavior added.

   Diagnostic Removals
       o   "Ambiguous use of -foo resolved as -&foo()"

           There is actually no ambiguity here, and this impedes the use of
           negated constants; e.g., "-Inf".

       o   "Constant is not a FOO reference"

           Compile-time checking of constant dereferencing (e.g.,
           "my_constant->()") has been removed, since it was not taking
           overloading into account.  [perl #69456]
           <https://rt.perl.org/Ticket/Display.html?id=69456> [perl #122607]
           <https://rt.perl.org/Ticket/Display.html?id=122607>


Utility Changes

   find2perl, s2p and a2p removal
       o   The x2p/ directory has been removed from the Perl core.

           This removes find2perl, s2p and a2p. They have all been released to
           CPAN as separate distributions ("App::find2perl", "App::s2p",
           "App::a2p").

   h2ph
       o   h2ph now handles hexadecimal constants in the compiler's predefined
           macro definitions, as visible in $Config{cppsymbols}.  [perl
           #123784] <https://rt.perl.org/Ticket/Display.html?id=123784>.

   encguess
       o   No longer depends on non-core modules.


Configuration and Compilation

       o   Configure now checks for "lrintl()", "lroundl()", "llrintl()", and
           "llroundl()".

       o   Configure with "-Dmksymlinks" should now be faster.  [perl #122002]
           <https://rt.perl.org/Ticket/Display.html?id=122002>.

       o   The "pthreads" and "cl" libraries will be linked by default if
           present.  This allows XS modules that require threading to work on
           non-threaded perls. Note that you must still pass "-Dusethreads" if
           you want a threaded perl.

       o   To get more precision and range for floating point numbers one can
           now use the GCC quadmath library which implements the quadruple
           precision floating point numbers on x86 and IA-64 platforms.  See
           INSTALL for details.

       o   MurmurHash64A and MurmurHash64B can now be configured as the
           internal hash function.

       o   "make test.valgrind" now supports parallel testing.

           For example:

               TEST_JOBS=9 make test.valgrind

           See "valgrind" in perlhacktips for more information.

           [perl #121431] <https://rt.perl.org/Ticket/Display.html?id=121431>

       o   The MAD (Misc Attribute Decoration) build option has been removed

           This was an unmaintained attempt at preserving the Perl parse tree
           more faithfully so that automatic conversion of Perl 5 to Perl 6
           would have been easier.

           This build-time configuration option had been unmaintained for
           years, and had probably seriously diverged on both Perl 5 and Perl
           6 sides.

       o   A new compilation flag, "-DPERL_OP_PARENT" is available. For
           details, see the discussion below at "Internal Changes".

       o   Pathtools no longer tries to load XS on miniperl. This speeds up
           building perl slightly.


Testing

       o   t/porting/re_context.t has been added to test that utf8 and its
           dependencies only use the subset of the "$1..$n" capture vars that
           "Perl_save_re_context()" is hard-coded to localize, because that
           function has no efficient way of determining at runtime what vars
           to localize.

       o   Tests for performance issues have been added in the file
           t/perf/taint.t.

       o   Some regular expression tests are written in such a way that they
           will run very slowly if certain optimizations break. These tests
           have been moved into new files, t/re/speed.t and t/re/speed_thr.t,
           and are run with a "watchdog()".

       o   "test.pl" now allows "plan skip_all => $reason", to make it more
           compatible with "Test::More".

       o   A new test script, op/infnan.t, has been added to test if infinity
           and NaN are working correctly.  See "Infinity and NaN (not-a-
           number) handling improved".


Platform Support

   Regained Platforms
       IRIX and Tru64 platforms are working again.
           Some "make test" failures remain: [perl #123977]
           <https://rt.perl.org/Ticket/Display.html?id=123977> and [perl
           #125298] <https://rt.perl.org/Ticket/Display.html?id=125298> for
           IRIX; [perl #124212]
           <https://rt.perl.org/Ticket/Display.html?id=124212>, [cpan #99605]
           <https://rt.cpan.org/Public/Bug/Display.html?id=99605>, and [cpan
           #104836] <https://rt.cpan.org/Ticket/Display.html?id=104836> for
           Tru64.

       z/OS running EBCDIC Code Page 1047
           Core perl now works on this EBCDIC platform.  Earlier perls also
           worked, but, even though support wasn't officially withdrawn,
           recent perls would not compile and run well.  Perl 5.20 would work,
           but had many bugs which have now been fixed.  Many CPAN modules
           that ship with Perl still fail tests, including "Pod::Simple".
           However the version of "Pod::Simple" currently on CPAN should work;
           it was fixed too late to include in Perl 5.22.  Work is under way
           to fix many of the still-broken CPAN modules, which likely will be
           installed on CPAN when completed, so that you may not have to wait
           until Perl 5.24 to get a working version.

   Discontinued Platforms
       NeXTSTEP/OPENSTEP
           NeXTSTEP was a proprietary operating system bundled with NeXT's
           workstations in the early to mid 90s; OPENSTEP was an API
           specification that provided a NeXTSTEP-like environment on a non-
           NeXTSTEP system.  Both are now long dead, so support for building
           Perl on them has been removed.

   Platform-Specific Notes
       EBCDIC
           Special handling is required of the perl interpreter on EBCDIC
           platforms to get "qr/[i-j]/" to match only "i" and "j", since there
           are 7 characters between the code points for "i" and "j".  This
           special handling had only been invoked when both ends of the range
           are literals.  Now it is also invoked if any of the "\N{...}" forms
           for specifying a character by name or Unicode code point is used
           instead of a literal.  See "Character Ranges" in perlrecharclass.

       HP-UX
           The archname now distinguishes use64bitint from use64bitall.

       Android
           Build support has been improved for cross-compiling in general and
           for Android in particular.

       VMS
           o   When spawning a subprocess without waiting, the return value is
               now the correct PID.

           o   Fix a prototype so linking doesn't fail under the VMS C++
               compiler.

           o   "finite", "finitel", and "isfinite" detection has been added to
               "configure.com", environment handling has had some minor
               changes, and a fix for legacy feature checking status.

       Win32
           o   miniperl.exe is now built with "-fno-strict-aliasing", allowing
               64-bit builds to complete on GCC 4.8.  [perl #123976]
               <https://rt.perl.org/Ticket/Display.html?id=123976>

           o   "nmake minitest" now works on Win32.  Due to dependency issues
               you need to build "nmake test-prep" first, and a small number
               of the tests fail.  [perl #123394]
               <https://rt.perl.org/Ticket/Display.html?id=123394>

           o   Perl can now be built in C++ mode on Windows by setting the
               makefile macro "USE_CPLUSPLUS" to the value "define".

           o   The list form of piped open has been implemented for Win32.
               Note: unlike "system LIST" this does not fall back to the
               shell.  [perl #121159]
               <https://rt.perl.org/Ticket/Display.html?id=121159>

           o   New "DebugSymbols" and "DebugFull" configuration options added
               to Windows makefiles.

           o   Previously, compiling XS modules (including CPAN ones) using
               Visual C++ for Win64 resulted in around a dozen warnings per
               file from hv_func.h.  These warnings have been silenced.

           o   Support for building without PerlIO has been removed from the
               Windows makefiles.  Non-PerlIO builds were all but deprecated
               in Perl 5.18.0 and are already not supported by Configure on
               POSIX systems.

           o   Between 2 and 6 milliseconds and seven I/O calls have been
               saved per attempt to open a perl module for each path in @INC.

           o   Intel C builds are now always built with C99 mode on.

           o   %I64d is now being used instead of %lld for MinGW.

           o   In the experimental ":win32" layer, a crash in "open" was
               fixed. Also opening /dev/null (which works under Win32 Perl's
               default ":unix" layer) was implemented for ":win32".  [perl
               #122224] <https://rt.perl.org/Ticket/Display.html?id=122224>

           o   A new makefile option, "USE_LONG_DOUBLE", has been added to the
               Windows dmake makefile for gcc builds only.  Set this to
               "define" if you want perl to use long doubles to give more
               accuracy and range for floating point numbers.

       OpenBSD
           On OpenBSD, Perl will now default to using the system "malloc" due
           to the security features it provides. Perl's own malloc wrapper has
           been in use since v5.14 due to performance reasons, but the OpenBSD
           project believes the tradeoff is worth it and would prefer that
           users who need the speed specifically ask for it.

           [perl #122000] <https://rt.perl.org/Ticket/Display.html?id=122000>.

       Solaris
           o   We now look for the Sun Studio compiler in both /opt/solstudio*
               and /opt/solarisstudio*.

           o   Builds on Solaris 10 with "-Dusedtrace" would fail early since
               make didn't follow implied dependencies to build
               "perldtrace.h".  Added an explicit dependency to "depend".
               [perl #120120]
               <https://rt.perl.org/Ticket/Display.html?id=120120>

           o   C99 options have been cleaned up; hints look for "solstudio" as
               well as "SUNWspro"; and support for native "setenv" has been
               added.


Internal Changes

       o   Experimental support has been added to allow ops in the optree to
           locate their parent, if any. This is enabled by the non-default
           build option "-DPERL_OP_PARENT". It is envisaged that this will
           eventually become enabled by default, so XS code which directly
           accesses the "op_sibling" field of ops should be updated to be
           future-proofed.

           On "PERL_OP_PARENT" builds, the "op_sibling" field has been renamed
           "op_sibparent" and a new flag, "op_moresib", added. On the last op
           in a sibling chain, "op_moresib" is false and "op_sibparent" points
           to the parent (if any) rather than being "NULL".

           To make existing code work transparently whether using
           "PERL_OP_PARENT" or not, a number of new macros and functions have
           been added that should be used, rather than directly manipulating
           "op_sibling".

           For the case of just reading "op_sibling" to determine the next
           sibling, two new macros have been added. A simple scan through a
           sibling chain like this:

               for (; kid->op_sibling; kid = kid->op_sibling) { ... }

           should now be written as:

               for (; OpHAS_SIBLING(kid); kid = OpSIBLING(kid)) { ... }

           For altering optrees, a general-purpose function
           "op_sibling_splice()" has been added, which allows for manipulation
           of a chain of sibling ops.  By analogy with the Perl function
           "splice()", it allows you to cut out zero or more ops from a
           sibling chain and replace them with zero or more new ops.  It
           transparently handles all the updating of sibling, parent, op_last
           pointers etc.

           If you need to manipulate ops at a lower level, then three new
           macros, "OpMORESIB_set", "OpLASTSIB_set" and "OpMAYBESIB_set" are
           intended to be a low-level portable way to set "op_sibling" /
           "op_sibparent" while also updating "op_moresib".  The first sets
           the sibling pointer to a new sibling, the second makes the op the
           last sibling, and the third conditionally does the first or second
           action.  Note that unlike "op_sibling_splice()" these macros won't
           maintain consistency in the parent at the same time (e.g. by
           updating "op_first" and "op_last" where appropriate).

           A C-level "Perl_op_parent()" function and a Perl-level
           "B::OP::parent()" method have been added. The C function only
           exists under "PERL_OP_PARENT" builds (using it is build-time error
           on vanilla perls).  "B::OP::parent()" exists always, but on a
           vanilla build it always returns "NULL". Under "PERL_OP_PARENT",
           they return the parent of the current op, if any. The variable
           $B::OP::does_parent allows you to determine whether "B" supports
           retrieving an op's parent.

           "PERL_OP_PARENT" was introduced in 5.21.2, but the interface was
           changed considerably in 5.21.11. If you updated your code before
           the 5.21.11 changes, it may require further revision. The main
           changes after 5.21.2 were:

           o   The "OP_SIBLING" and "OP_HAS_SIBLING" macros have been renamed
               "OpSIBLING" and "OpHAS_SIBLING" for consistency with other op-
               manipulating macros.

           o   The "op_lastsib" field has been renamed "op_moresib", and its
               meaning inverted.

           o   The macro "OpSIBLING_set" has been removed, and has been
               superseded by "OpMORESIB_set" et al.

           o   The "op_sibling_splice()" function now accepts a null "parent"
               argument where the splicing doesn't affect the first or last
               ops in the sibling chain

       o   Macros have been created to allow XS code to better manipulate the
           POSIX locale category "LC_NUMERIC".  See "Locale-related functions
           and macros" in perlapi.

       o   The previous "atoi" et al replacement function, "grok_atou", has
           now been superseded by "grok_atoUV".  See perlclib for details.

       o   A new function, "Perl_sv_get_backrefs()", has been added which
           allows you retrieve the weak references, if any, which point at an
           SV.

       o   The "screaminstr()" function has been removed. Although marked as
           public API, it was undocumented and had no usage in CPAN modules.
           Calling it has been fatal since 5.17.0.

       o   The "newDEFSVOP()", "block_start()", "block_end()" and "intro_my()"
           functions have been added to the API.

       o   The internal "convert" function in op.c has been renamed
           "op_convert_list" and added to the API.

       o   The "sv_magic()" function no longer forbids "ext" magic on read-
           only values.  After all, perl can't know whether the custom magic
           will modify the SV or not.  [perl #123103]
           <https://rt.perl.org/Ticket/Display.html?id=123103>.

       o   Accessing "CvPADLIST" in perlapi on an XSUB is now forbidden.

           The "CvPADLIST" field has been reused for a different internal
           purpose for XSUBs. So in particular, you can no longer rely on it
           being NULL as a test of whether a CV is an XSUB. Use "CvISXSUB()"
           instead.

       o   SVs of type "SVt_NV" are now sometimes bodiless when the build
           configuration and platform allow it: specifically, when "sizeof(NV)
           <= sizeof(IV)". "Bodiless" means that the NV value is stored
           directly in the head of an SV, without requiring a separate body to
           be allocated. This trick has already been used for IVs since 5.9.2
           (though in the case of IVs, it is always used, regardless of
           platform and build configuration).

       o   The $DB::single, $DB::signal and $DB::trace variables now have set-
           and get-magic that stores their values as IVs, and those IVs are
           used when testing their values in "pp_dbstate()".  This prevents
           perl from recursing infinitely if an overloaded object is assigned
           to any of those variables.  [perl #122445]
           <https://rt.perl.org/Ticket/Display.html?id=122445>.

       o   "Perl_tmps_grow()", which is marked as public API but is
           undocumented, has been removed from the public API. This change
           does not affect XS code that uses the "EXTEND_MORTAL" macro to pre-
           extend the mortal stack.

       o   Perl's internals no longer sets or uses the "SVs_PADMY" flag.
           "SvPADMY()" now returns a true value for anything not marked
           "PADTMP" and "SVs_PADMY" is now defined as 0.

       o   The macros "SETsv" and "SETsvUN" have been removed. They were no
           longer used in the core since commit 6f1401dc2a five years ago, and
           have not been found present on CPAN.

       o   The "SvFAKE" bit (unused on HVs) got informally reserved by David
           Mitchell for future work on vtables.

       o   The "sv_catpvn_flags()" function accepts "SV_CATBYTES" and
           "SV_CATUTF8" flags, which specify whether the appended string is
           bytes or UTF-8, respectively. (These flags have in fact been
           present since 5.16.0, but were formerly not regarded as part of the
           API.)

       o   A new opcode class, "METHOP", has been introduced. It holds
           information used at runtime to improve the performance of
           class/object method calls.

           "OP_METHOD" and "OP_METHOD_NAMED" have changed from being
           "UNOP/SVOP" to being "METHOP".

       o   "cv_name()" is a new API function that can be passed a CV or GV.
           It returns an SV containing the name of the subroutine, for use in
           diagnostics.

           [perl #116735] <https://rt.perl.org/Ticket/Display.html?id=116735>
           [perl #120441] <https://rt.perl.org/Ticket/Display.html?id=120441>

       o   "cv_set_call_checker_flags()" is a new API function that works like
           "cv_set_call_checker()", except that it allows the caller to
           specify whether the call checker requires a full GV for reporting
           the subroutine's name, or whether it could be passed a CV instead.
           Whatever value is passed will be acceptable to "cv_name()".
           "cv_set_call_checker()" guarantees there will be a GV, but it may
           have to create one on the fly, which is inefficient.  [perl
           #116735] <https://rt.perl.org/Ticket/Display.html?id=116735>

       o   "CvGV" (which is not part of the API) is now a more complex macro,
           which may call a function and reify a GV.  For those cases where it
           has been used as a boolean, "CvHASGV" has been added, which will
           return true for CVs that notionally have GVs, but without reifying
           the GV.  "CvGV" also returns a GV now for lexical subs.  [perl
           #120441] <https://rt.perl.org/Ticket/Display.html?id=120441>

       o   The "sync_locale" in perlapi function has been added to the public
           API.  Changing the program's locale should be avoided by XS code.
           Nevertheless, certain non-Perl libraries called from XS need to do
           so, such as "Gtk".  When this happens, Perl needs to be told that
           the locale has changed.  Use this function to do so, before
           returning to Perl.

       o   The defines and labels for the flags in the "op_private" field of
           OPs are now auto-generated from data in regen/op_private.  The
           noticeable effect of this is that some of the flag output of
           "Concise" might differ slightly, and the flag output of "perl -Dx"
           may differ considerably (they both use the same set of labels now).
           Also, debugging builds now have a new assertion in "op_free()" to
           ensure that the op doesn't have any unrecognized flags set in
           "op_private".

       o   The deprecated variable "PL_sv_objcount" has been removed.

       o   Perl now tries to keep the locale category "LC_NUMERIC" set to "C"
           except around operations that need it to be set to the program's
           underlying locale.  This protects the many XS modules that cannot
           cope with the decimal radix character not being a dot.  Prior to
           this release, Perl initialized this category to "C", but a call to
           "POSIX::setlocale()" would change it.  Now such a call will change
           the underlying locale of the "LC_NUMERIC" category for the program,
           but the locale exposed to XS code will remain "C".  There are new
           macros to manipulate the LC_NUMERIC locale, including
           "STORE_LC_NUMERIC_SET_TO_NEEDED" and
           "STORE_LC_NUMERIC_FORCE_TO_UNDERLYING".  See "Locale-related
           functions and macros" in perlapi.

       o   A new macro "isUTF8_CHAR" has been written which efficiently
           determines if the string given by its parameters begins with a
           well-formed UTF-8 encoded character.

       o   The following private API functions had their context parameter
           removed: "Perl_cast_ulong",  "Perl_cast_i32", "Perl_cast_iv",
           "Perl_cast_uv", "Perl_cv_const_sv", "Perl_mg_find",
           "Perl_mg_findext", "Perl_mg_magical", "Perl_mini_mktime",
           "Perl_my_dirfd", "Perl_sv_backoff", "Perl_utf8_hop".

           Note that the prefix-less versions of those functions that are part
           of the public API, such as "cast_i32()", remain unaffected.

       o   The "PADNAME" and "PADNAMELIST" types are now separate types, and
           no longer simply aliases for SV and AV.  [perl #123223]
           <https://rt.perl.org/Ticket/Display.html?id=123223>.

       o   Pad names are now always UTF-8.  The "PadnameUTF8" macro always
           returns true.  Previously, this was effectively the case already,
           but any support for two different internal representations of pad
           names has now been removed.

       o   A new op class, "UNOP_AUX", has been added. This is a subclass of
           "UNOP" with an "op_aux" field added, which points to an array of
           unions of UV, SV* etc. It is intended for where an op needs to
           store more data than a simple "op_sv" or whatever. Currently the
           only op of this type is "OP_MULTIDEREF" (see next item).

       o   A new op has been added, "OP_MULTIDEREF", which performs one or
           more nested array and hash lookups where the key is a constant or
           simple variable. For example the expression $a[0]{$k}[$i], which
           previously involved ten "rv2Xv", "Xelem", "gvsv" and "const" ops is
           now performed by a single "multideref" op. It can also handle
           "local", "exists" and "delete". A non-simple index expression, such
           as "[$i+1]" is still done using "aelem"/"helem", and single-level
           array lookup with a small constant index is still done using
           "aelemfast".


Selected Bug Fixes

       o   "close" now sets $!

           When an I/O error occurs, the fact that there has been an error is
           recorded in the handle.  "close" returns false for such a handle.
           Previously, the value of $! would be untouched by "close", so the
           common convention of writing "close $fh or die $!" did not work
           reliably.  Now the handle records the value of $!, too, and "close"
           restores it.

       o   "no re" now can turn off everything that "use re" enables

           Previously, running "no re" would turn off only a few things. Now
           it can turn off all the enabled things. For example, the only way
           to stop debugging, once enabled, was to exit the enclosing block;
           that is now fixed.

       o   "pack("D", $x)" and "pack("F", $x)" now zero the padding on x86
           long double builds.  Under some build options on GCC 4.8 and later,
           they used to either overwrite the zero-initialized padding, or
           bypass the initialized buffer entirely.  This caused op/pack.t to
           fail.  [perl #123971]
           <https://rt.perl.org/Ticket/Display.html?id=123971>

       o   Extending an array cloned from a parent thread could result in
           "Modification of a read-only value attempted" errors when
           attempting to modify the new elements.  [perl #124127]
           <https://rt.perl.org/Ticket/Display.html?id=124127>

       o   An assertion failure and subsequent crash with "*x=<y>" has been
           fixed.  [perl #123790]
           <https://rt.perl.org/Ticket/Display.html?id=123790>

       o   A possible crashing/looping bug related to compiling lexical subs
           has been fixed.  [perl #124099]
           <https://rt.perl.org/Ticket/Display.html?id=124099>

       o   UTF-8 now works correctly in function names, in unquoted HERE-
           document terminators, and in variable names used as array indexes.
           [perl #124113] <https://rt.perl.org/Ticket/Display.html?id=124113>

       o   Repeated global pattern matches in scalar context on large tainted
           strings were exponentially slow depending on the current match
           position in the string.  [perl #123202]
           <https://rt.perl.org/Ticket/Display.html?id=123202>

       o   Various crashes due to the parser getting confused by syntax errors
           have been fixed.  [perl #123801]
           <https://rt.perl.org/Ticket/Display.html?id=123801> [perl #123802]
           <https://rt.perl.org/Ticket/Display.html?id=123802> [perl #123955]
           <https://rt.perl.org/Ticket/Display.html?id=123955> [perl #123995]
           <https://rt.perl.org/Ticket/Display.html?id=123995>

       o   "split" in the scope of lexical $_ has been fixed not to fail
           assertions.  [perl #123763]
           <https://rt.perl.org/Ticket/Display.html?id=123763>

       o   "my $x : attr" syntax inside various list operators no longer fails
           assertions.  [perl #123817]
           <https://rt.perl.org/Ticket/Display.html?id=123817>

       o   An "@" sign in quotes followed by a non-ASCII digit (which is not a
           valid identifier) would cause the parser to crash, instead of
           simply trying the "@" as literal.  This has been fixed.  [perl
           #123963] <https://rt.perl.org/Ticket/Display.html?id=123963>

       o   "*bar::=*foo::=*glob_with_hash" has been crashing since Perl 5.14,
           but no longer does.  [perl #123847]
           <https://rt.perl.org/Ticket/Display.html?id=123847>

       o   "foreach" in scalar context was not pushing an item on to the
           stack, resulting in bugs.
           ("print 4, scalar do { foreach(@x){} } + 1" would print 5.)  It has
           been fixed to return "undef".  [perl #124004]
           <https://rt.perl.org/Ticket/Display.html?id=124004>

       o   Several cases of data used to store environment variable contents
           in core C code being potentially overwritten before being used have
           been fixed.  [perl #123748]
           <https://rt.perl.org/Ticket/Display.html?id=123748>

       o   Some patterns starting with "/.*..../" matched against long strings
           have been slow since v5.8, and some of the form "/.*..../i" have
           been slow since v5.18. They are now all fast again.  [perl #123743]
           <https://rt.perl.org/Ticket/Display.html?id=123743>.

       o   The original visible value of $/ is now preserved when it is set to
           an invalid value.  Previously if you set $/ to a reference to an
           array, for example, perl would produce a runtime error and not set
           "PL_rs", but Perl code that checked $/ would see the array
           reference.  [perl #123218]
           <https://rt.perl.org/Ticket/Display.html?id=123218>.

       o   In a regular expression pattern, a POSIX class, like "[:ascii:]",
           must be inside a bracketed character class, like "qr/[[:ascii:]]/".
           A warning is issued when something looking like a POSIX class is
           not inside a bracketed class.  That warning wasn't getting
           generated when the POSIX class was negated: "[:^ascii:]".  This is
           now fixed.

       o   Perl 5.14.0 introduced a bug whereby "eval { LABEL: }" would crash.
           This has been fixed.  [perl #123652]
           <https://rt.perl.org/Ticket/Display.html?id=123652>.

       o   Various crashes due to the parser getting confused by syntax errors
           have been fixed.  [perl #123617]
           <https://rt.perl.org/Ticket/Display.html?id=123617>.  [perl
           #123737] <https://rt.perl.org/Ticket/Display.html?id=123737>.
           [perl #123753] <https://rt.perl.org/Ticket/Display.html?id=123753>.
           [perl #123677] <https://rt.perl.org/Ticket/Display.html?id=123677>.

       o   Code like "/$a[/" used to read the next line of input and treat it
           as though it came immediately after the opening bracket.  Some
           invalid code consequently would parse and run, but some code caused
           crashes, so this is now disallowed.  [perl #123712]
           <https://rt.perl.org/Ticket/Display.html?id=123712>.

       o   Fix argument underflow for "pack".  [perl #123874]
           <https://rt.perl.org/Ticket/Display.html?id=123874>.

       o   Fix handling of non-strict "\x{}". Now "\x{}" is equivalent to
           "\x{0}" instead of faulting.

       o   "stat -t" is now no longer treated as stackable, just like "-t
           stat".  [perl #123816]
           <https://rt.perl.org/Ticket/Display.html?id=123816>.

       o   The following no longer causes a SEGV: "qr{x+(y(?0))*}".

       o   Fixed infinite loop in parsing backrefs in regexp patterns.

       o   Several minor bug fixes in behavior of Infinity and NaN, including
           warnings when stringifying Infinity-like or NaN-like strings. For
           example, "NaNcy" doesn't numify to NaN anymore.

       o   A bug in regular expression patterns that could lead to segfaults
           and other crashes has been fixed.  This occurred only in patterns
           compiled with "/i" while taking into account the current POSIX
           locale (which usually means they have to be compiled within the
           scope of "use locale"), and there must be a string of at least 128
           consecutive bytes to match.  [perl #123539]
           <https://rt.perl.org/Ticket/Display.html?id=123539>.

       o   "s///g" now works on very long strings (where there are more than 2
           billion iterations) instead of dying with 'Substitution loop'.
           [perl #103260] <https://rt.perl.org/Ticket/Display.html?id=103260>.
           [perl #123071] <https://rt.perl.org/Ticket/Display.html?id=123071>.

       o   "gmtime" no longer crashes with not-a-number values.  [perl
           #123495] <https://rt.perl.org/Ticket/Display.html?id=123495>.

       o   "\()" (a reference to an empty list), and "y///" with lexical $_ in
           scope, could both do a bad write past the end of the stack.  They
           have both been fixed to extend the stack first.

       o   "prototype()" with no arguments used to read the previous item on
           the stack, so "print "foo", prototype()" would print foo's
           prototype.  It has been fixed to infer $_ instead.  [perl #123514]
           <https://rt.perl.org/Ticket/Display.html?id=123514>.

       o   Some cases of lexical state subs declared inside predeclared subs
           could crash, for example when evalling a string including the name
           of an outer variable, but no longer do.

       o   Some cases of nested lexical state subs inside anonymous subs could
           cause 'Bizarre copy' errors or possibly even crashes.

       o   When trying to emit warnings, perl's default debugger (perl5db.pl)
           was sometimes giving 'Undefined subroutine &DB::db_warn called'
           instead.  This bug, which started to occur in Perl 5.18, has been
           fixed.  [perl #123553]
           <https://rt.perl.org/Ticket/Display.html?id=123553>.

       o   Certain syntax errors in substitutions, such as "s/${<>{})//",
           would crash, and had done so since Perl 5.10.  (In some cases the
           crash did not start happening till 5.16.)  The crash has, of
           course, been fixed.  [perl #123542]
           <https://rt.perl.org/Ticket/Display.html?id=123542>.

       o   Fix a couple of string grow size calculation overflows; in
           particular, a repeat expression like "33 x ~3" could cause a large
           buffer overflow since the new output buffer size was not correctly
           handled by "SvGROW()".  An expression like this now properly
           produces a memory wrap panic.  [perl #123554]
           <https://rt.perl.org/Ticket/Display.html?id=123554>.

       o   "formline("@...", "a");" would crash.  The "FF_CHECKNL" case in
           "pp_formline()" didn't set the pointer used to mark the chop
           position, which led to the "FF_MORE" case crashing with a
           segmentation fault.  This has been fixed.  [perl #123538]
           <https://rt.perl.org/Ticket/Display.html?id=123538>.

       o   A possible buffer overrun and crash when parsing a literal pattern
           during regular expression compilation has been fixed.  [perl
           #123604] <https://rt.perl.org/Ticket/Display.html?id=123604>.

       o   "fchmod()" and "futimes()" now set $! when they fail due to being
           passed a closed file handle.  [perl #122703]
           <https://rt.perl.org/Ticket/Display.html?id=122703>.

       o   "op_free()" and "scalarvoid()" no longer crash due to a stack
           overflow when freeing a deeply recursive op tree.  [perl #108276]
           <https://rt.perl.org/Ticket/Display.html?id=108276>.

       o   In Perl 5.20.0, $^N accidentally had the internal UTF-8 flag turned
           off if accessed from a code block within a regular expression,
           effectively UTF-8-encoding the value.  This has been fixed.  [perl
           #123135] <https://rt.perl.org/Ticket/Display.html?id=123135>.

       o   A failed "semctl" call no longer overwrites existing items on the
           stack, which means that "(semctl(-1,0,0,0))[0]" no longer gives an
           "uninitialized" warning.

       o   "else{foo()}" with no space before "foo" is now better at assigning
           the right line number to that statement.  [perl #122695]
           <https://rt.perl.org/Ticket/Display.html?id=122695>.

       o   Sometimes the assignment in "@array = split" gets optimised so that
           "split" itself writes directly to the array.  This caused a bug,
           preventing this assignment from being used in lvalue context.  So
           "(@a=split//,"foo")=bar()" was an error.  (This bug probably goes
           back to Perl 3, when the optimisation was added.) It has now been
           fixed.  [perl #123057]
           <https://rt.perl.org/Ticket/Display.html?id=123057>.

       o   When an argument list fails the checks specified by a subroutine
           signature (which is still an experimental feature), the resulting
           error messages now give the file and line number of the caller, not
           of the called subroutine.  [perl #121374]
           <https://rt.perl.org/Ticket/Display.html?id=121374>.

       o   The flip-flop operators (".." and "..." in scalar context) used to
           maintain a separate state for each recursion level (the number of
           times the enclosing sub was called recursively), contrary to the
           documentation.  Now each closure has one internal state for each
           flip-flop.  [perl #122829]
           <https://rt.perl.org/Ticket/Display.html?id=122829>.

       o   The flip-flop operator (".." in scalar context) would return the
           same scalar each time, unless the containing subroutine was called
           recursively.  Now it always returns a new scalar.  [perl #122829]
           <https://rt.perl.org/Ticket/Display.html?id=122829>.

       o   "use", "no", statement labels, special blocks ("BEGIN") and pod are
           now permitted as the first thing in a "map" or "grep" block, the
           block after "print" or "say" (or other functions) returning a
           handle, and within "${...}", "@{...}", etc.  [perl #122782]
           <https://rt.perl.org/Ticket/Display.html?id=122782>.

       o   The repetition operator "x" now propagates lvalue context to its
           left-hand argument when used in contexts like "foreach".  That
           allows "for(($#that_array)x2) { ... }" to work as expected if the
           loop modifies $_.

       o   "(...) x ..." in scalar context used to corrupt the stack if one
           operand was an object with "x" overloading, causing erratic
           behavior.  [perl #121827]
           <https://rt.perl.org/Ticket/Display.html?id=121827>.

       o   Assignment to a lexical scalar is often optimised away; for example
           in "my $x; $x = $y + $z", the assign operator is optimised away and
           the add operator writes its result directly to $x.  Various bugs
           related to this optimisation have been fixed.  Certain operators on
           the right-hand side would sometimes fail to assign the value at all
           or assign the wrong value, or would call STORE twice or not at all
           on tied variables.  The operators affected were "$foo++", "$foo--",
           and "-$foo" under "use integer", "chomp", "chr" and "setpgrp".

       o   List assignments were sometimes buggy if the same scalar ended up
           on both sides of the assignment due to use of "tied", "values" or
           "each".  The result would be the wrong value getting assigned.

       o   "setpgrp($nonzero)" (with one argument) was accidentally changed in
           5.16 to mean setpgrp(0).  This has been fixed.

       o   "__SUB__" could return the wrong value or even corrupt memory under
           the debugger (the "-d" switch) and in subs containing "eval
           $string".

       o   When "sub () { $var }" becomes inlinable, it now returns a
           different scalar each time, just as a non-inlinable sub would,
           though Perl still optimises the copy away in cases where it would
           make no observable difference.

       o   "my sub f () { $var }" and "sub () : attr { $var }" are no longer
           eligible for inlining.  The former would crash; the latter would
           just throw the attributes away.  An exception is made for the
           little-known ":method" attribute, which does nothing much.

       o   Inlining of subs with an empty prototype is now more consistent
           than before. Previously, a sub with multiple statements, of which
           all but the last were optimised away, would be inlinable only if it
           were an anonymous sub containing a string "eval" or "state"
           declaration or closing over an outer lexical variable (or any
           anonymous sub under the debugger).  Now any sub that gets folded to
           a single constant after statements have been optimised away is
           eligible for inlining.  This applies to things like "sub () {
           jabber() if DEBUG; 42 }".

           Some subroutines with an explicit "return" were being made
           inlinable, contrary to the documentation,  Now "return" always
           prevents inlining.

       o   On some systems, such as VMS, "crypt" can return a non-ASCII
           string.  If a scalar assigned to had contained a UTF-8 string
           previously, then "crypt" would not turn off the UTF-8 flag, thus
           corrupting the return value.  This would happen with
           "$lexical = crypt ...".

       o   "crypt" no longer calls "FETCH" twice on a tied first argument.

       o   An unterminated here-doc on the last line of a quote-like operator
           ("qq[${ <<END }]", "/(?{ <<END })/") no longer causes a double
           free.  It started doing so in 5.18.

       o   "index()" and "rindex()" no longer crash when used on strings over
           2GB in size.  [perl #121562]
           <https://rt.perl.org/Ticket/Display.html?id=121562>.

       o   A small, previously intentional, memory leak in
           "PERL_SYS_INIT"/"PERL_SYS_INIT3" on Win32 builds was fixed. This
           might affect embedders who repeatedly create and destroy perl
           engines within the same process.

       o   "POSIX::localeconv()" now returns the data for the program's
           underlying locale even when called from outside the scope of
           "use locale".

       o   "POSIX::localeconv()" now works properly on platforms which don't
           have "LC_NUMERIC" and/or "LC_MONETARY", or for which Perl has been
           compiled to disregard either or both of these locale categories.
           In such circumstances, there are now no entries for the
           corresponding values in the hash returned by "localeconv()".

       o   "POSIX::localeconv()" now marks appropriately the values it returns
           as UTF-8 or not.  Previously they were always returned as bytes,
           even if they were supposed to be encoded as UTF-8.

       o   On Microsoft Windows, within the scope of "use locale", the
           following POSIX character classes gave results for many locales
           that did not conform to the POSIX standard: "[[:alnum:]]",
           "[[:alpha:]]", "[[:blank:]]", "[[:digit:]]", "[[:graph:]]",
           "[[:lower:]]", "[[:print:]]", "[[:punct:]]", "[[:upper:]]",
           "[[:word:]]", and "[[:xdigit:]]".  This was because the underlying
           Microsoft implementation does not follow the standard.  Perl now
           takes special precautions to correct for this.

       o   Many issues have been detected by Coverity
           <http://www.coverity.com/> and fixed.

       o   "system()" and friends should now work properly on more Android
           builds.

           Due to an oversight, the value specified through "-Dtargetsh" to
           Configure would end up being ignored by some of the build process.
           This caused perls cross-compiled for Android to end up with
           defective versions of "system()", "exec()" and backticks: the
           commands would end up looking for "/bin/sh" instead of
           "/system/bin/sh", and so would fail for the vast majority of
           devices, leaving $! as "ENOENT".

       o   "qr(...\(...\)...)", "qr[...\[...\]...]", and "qr{...\{...\}...}"
           now work.  Previously it was impossible to escape these three left-
           characters with a backslash within a regular expression pattern
           where otherwise they would be considered metacharacters, and the
           pattern opening delimiter was the character, and the closing
           delimiter was its mirror character.

       o   "s///e" on tainted UTF-8 strings corrupted "pos()". This bug,
           introduced in 5.20, is now fixed.  [perl #122148]
           <https://rt.perl.org/Ticket/Display.html?id=122148>.

       o   A non-word boundary in a regular expression ("\B") did not always
           match the end of the string; in particular "q{} =~ /\B/" did not
           match. This bug, introduced in perl 5.14, is now fixed.  [perl
           #122090] <https://rt.perl.org/Ticket/Display.html?id=122090>.

       o   "" P" =~ /(?=.*P)P/" should match, but did not. This is now fixed.
           [perl #122171] <https://rt.perl.org/Ticket/Display.html?id=122171>.

       o   Failing to compile "use Foo" in an "eval" could leave a spurious
           "BEGIN" subroutine definition, which would produce a "Subroutine
           BEGIN redefined" warning on the next use of "use", or other "BEGIN"
           block.  [perl #122107]
           <https://rt.perl.org/Ticket/Display.html?id=122107>.

       o   "method { BLOCK } ARGS" syntax now correctly parses the arguments
           if they begin with an opening brace.  [perl #46947]
           <https://rt.perl.org/Ticket/Display.html?id=46947>.

       o   External libraries and Perl may have different ideas of what the
           locale is.  This is problematic when parsing version strings if the
           locale's numeric separator has been changed.  Version parsing has
           been patched to ensure it handles the locales correctly.  [perl
           #121930] <https://rt.perl.org/Ticket/Display.html?id=121930>.

       o   A bug has been fixed where zero-length assertions and code blocks
           inside of a regex could cause "pos" to see an incorrect value.
           [perl #122460] <https://rt.perl.org/Ticket/Display.html?id=122460>.

       o   Dereferencing of constants now works correctly for typeglob
           constants.  Previously the glob was stringified and its name looked
           up.  Now the glob itself is used.  [perl #69456]
           <https://rt.perl.org/Ticket/Display.html?id=69456>

       o   When parsing a sigil ("$" "@" "%" "&)" followed by braces, the
           parser no longer tries to guess whether it is a block or a hash
           constructor (causing a syntax error when it guesses the latter),
           since it can only be a block.

       o   "undef $reference" now frees the referent immediately, instead of
           hanging on to it until the next statement.  [perl #122556]
           <https://rt.perl.org/Ticket/Display.html?id=122556>

       o   Various cases where the name of a sub is used (autoload,
           overloading, error messages) used to crash for lexical subs, but
           have been fixed.

       o   Bareword lookup now tries to avoid vivifying packages if it turns
           out the bareword is not going to be a subroutine name.

       o   Compilation of anonymous constants (e.g., "sub () { 3 }") no longer
           deletes any subroutine named "__ANON__" in the current package.
           Not only was "*__ANON__{CODE}" cleared, but there was a memory
           leak, too.  This bug goes back to Perl 5.8.0.

       o   Stub declarations like "sub f;" and "sub f ();" no longer wipe out
           constants of the same name declared by "use constant".  This bug
           was introduced in Perl 5.10.0.

       o   "qr/[\N{named sequence}]/" now works properly in many instances.

           Some names known to "\N{...}" refer to a sequence of multiple
           characters, instead of the usual single character.  Bracketed
           character classes generally only match single characters, but now
           special handling has been added so that they can match named
           sequences, but not if the class is inverted or the sequence is
           specified as the beginning or end of a range.  In these cases, the
           only behavior change from before is a slight rewording of the fatal
           error message given when this class is part of a "?[...])"
           construct.  When the "[...]"  stands alone, the same non-fatal
           warning as before is raised, and only the first character in the
           sequence is used, again just as before.

       o   Tainted constants evaluated at compile time no longer cause
           unrelated statements to become tainted.  [perl #122669]
           <https://rt.perl.org/Ticket/Display.html?id=122669>

       o   "open $$fh, ...", which vivifies a handle with a name like
           "main::_GEN_0", was not giving the handle the right reference
           count, so a double free could happen.

       o   When deciding that a bareword was a method name, the parser would
           get confused if an "our" sub with the same name existed, and look
           up the method in the package of the "our" sub, instead of the
           package of the invocant.

       o   The parser no longer gets confused by "\U=" within a double-quoted
           string.  It used to produce a syntax error, but now compiles it
           correctly.  [perl #80368]
           <https://rt.perl.org/Ticket/Display.html?id=80368>

       o   It has always been the intention for the "-B" and "-T" file test
           operators to treat UTF-8 encoded files as text.  (perlfunc has been
           updated to say this.)  Previously, it was possible for some files
           to be considered UTF-8 that actually weren't valid UTF-8.  This is
           now fixed.  The operators now work on EBCDIC platforms as well.

       o   Under some conditions warning messages raised during regular
           expression pattern compilation were being output more than once.
           This has now been fixed.

       o   Perl 5.20.0 introduced a regression in which a UTF-8 encoded
           regular expression pattern that contains a single ASCII lowercase
           letter did not match its uppercase counterpart. That has been fixed
           in both 5.20.1 and 5.22.0.  [perl #122655]
           <https://rt.perl.org/Ticket/Display.html?id=122655>

       o   Constant folding could incorrectly suppress warnings if lexical
           warnings ("use warnings" or "no warnings") were not in effect and
           $^W were false at compile time and true at run time.

       o   Loading Unicode tables during a regular expression match could
           cause assertion failures under debugging builds if the previous
           match used the very same regular expression.  [perl #122747]
           <https://rt.perl.org/Ticket/Display.html?id=122747>

       o   Thread cloning used to work incorrectly for lexical subs, possibly
           causing crashes or double frees on exit.

       o   Since Perl 5.14.0, deleting $SomePackage::{__ANON__} and then
           undefining an anonymous subroutine could corrupt things internally,
           resulting in Devel::Peek crashing or B.pm giving nonsensical data.
           This has been fixed.

       o   "(caller $n)[3]" now reports names of lexical subs, instead of
           treating them as "(unknown)".

       o   "sort subname LIST" now supports using a lexical sub as the
           comparison routine.

       o   Aliasing (e.g., via "*x = *y") could confuse list assignments that
           mention the two names for the same variable on either side, causing
           wrong values to be assigned.  [perl #15667]
           <https://rt.perl.org/Ticket/Display.html?id=15667>

       o   Long here-doc terminators could cause a bad read on short lines of
           input.  This has been fixed.  It is doubtful that any crash could
           have occurred.  This bug goes back to when here-docs were
           introduced in Perl 3.000 twenty-five years ago.

       o   An optimization in "split" to treat "split /^/" like "split /^/m"
           had the unfortunate side-effect of also treating "split /\A/" like
           "split /^/m", which it should not.  This has been fixed.  (Note,
           however, that "split /^x/" does not behave like "split /^x/m",
           which is also considered to be a bug and will be fixed in a future
           version.)  [perl #122761]
           <https://rt.perl.org/Ticket/Display.html?id=122761>

       o   The little-known "my Class $var" syntax (see fields and attributes)
           could get confused in the scope of "use utf8" if "Class" were a
           constant whose value contained Latin-1 characters.

       o   Locking and unlocking values via Hash::Util or
           "Internals::SvREADONLY" no longer has any effect on values that
           were read-only to begin with.  Previously, unlocking such values
           could result in crashes, hangs or other erratic behavior.

       o   Some unterminated "(?(...)...)" constructs in regular expressions
           would either crash or give erroneous error messages.  "/(?(1)/" is
           one such example.

       o   "pack "w", $tied" no longer calls FETCH twice.

       o   List assignments like "($x, $z) = (1, $y)" now work correctly if $x
           and $y have been aliased by "foreach".

       o   Some patterns including code blocks with syntax errors, such as
           "/ (?{(^{})/", would hang or fail assertions on debugging builds.
           Now they produce errors.

       o   An assertion failure when parsing "sort" with debugging enabled has
           been fixed.  [perl #122771]
           <https://rt.perl.org/Ticket/Display.html?id=122771>.

       o   "*a = *b; @a = split //, $b[1]" could do a bad read and produce
           junk results.

       o   In "() = @array = split", the "() =" at the beginning no longer
           confuses the optimizer into assuming a limit of 1.

       o   Fatal warnings no longer prevent the output of syntax errors.
           [perl #122966] <https://rt.perl.org/Ticket/Display.html?id=122966>.

       o   Fixed a NaN double-to-long-double conversion error on VMS. For
           quiet NaNs (and only on Itanium, not Alpha) negative infinity
           instead of NaN was produced.

       o   Fixed the issue that caused "make distclean" to incorrectly leave
           some files behind.  [perl #122820]
           <https://rt.perl.org/Ticket/Display.html?id=122820>.

       o   AIX now sets the length in "getsockopt" correctly.  [perl #120835]
           <https://rt.perl.org/Ticket/Display.html?id=120835>.  [cpan #91183]
           <https://rt.cpan.org/Ticket/Display.html?id=91183>.  [cpan #85570]
           <https://rt.cpan.org/Ticket/Display.html?id=85570>.

       o   The optimization phase of a regexp compilation could run "forever"
           and exhaust all memory under certain circumstances; now fixed.
           [perl #122283] <https://rt.perl.org/Ticket/Display.html?id=122283>.

       o   The test script t/op/crypt.t now uses the SHA-256 algorithm if the
           default one is disabled, rather than giving failures.  [perl
           #121591] <https://rt.perl.org/Ticket/Display.html?id=121591>.

       o   Fixed an off-by-one error when setting the size of a shared array.
           [perl #122950] <https://rt.perl.org/Ticket/Display.html?id=122950>.

       o   Fixed a bug that could cause perl to enter an infinite loop during
           compilation. In particular, a while(1) within a sublist, e.g.

               sub foo { () = ($a, my $b, ($c, do { while(1) {} })) }

           The bug was introduced in 5.20.0 [perl #122995]
           <https://rt.perl.org/Ticket/Display.html?id=122995>.

       o   On Win32, if a variable was "local"-ized in a pseudo-process that
           later forked, restoring the original value in the child pseudo-
           process caused memory corruption and a crash in the child pseudo-
           process (and therefore the OS process).  [perl #40565]
           <https://rt.perl.org/Ticket/Display.html?id=40565>.

       o   Calling "write" on a format with a "^**" field could produce a
           panic in "sv_chop()" if there were insufficient arguments or if the
           variable used to fill the field was empty.  [perl #123245]
           <https://rt.perl.org/Ticket/Display.html?id=123245>.

       o   Non-ASCII lexical sub names now appear without trailing junk when
           they appear in error messages.

       o   The "\@" subroutine prototype no longer flattens parenthesized
           arrays (taking a reference to each element), but takes a reference
           to the array itself.  [perl #47363]
           <https://rt.perl.org/Ticket/Display.html?id=47363>.

       o   A block containing nothing except a C-style "for" loop could
           corrupt the stack, causing lists outside the block to lose elements
           or have elements overwritten.  This could happen with "map {
           for(...){...} } ..." and with lists containing "do { for(...){...}
           }".  [perl #123286]
           <https://rt.perl.org/Ticket/Display.html?id=123286>.

       o   "scalar()" now propagates lvalue context, so that
           "for(scalar($#foo)) { ... }" can modify $#foo through $_.

       o   "qr/@array(?{block})/" no longer dies with "Bizarre copy of ARRAY".
           [perl #123344] <https://rt.perl.org/Ticket/Display.html?id=123344>.

       o   "eval '$variable'" in nested named subroutines would sometimes look
           up a global variable even with a lexical variable in scope.

       o   In perl 5.20.0, "sort CORE::fake" where 'fake' is anything other
           than a keyword, started chopping off the last 6 characters and
           treating the result as a sort sub name.  The previous behavior of
           treating "CORE::fake" as a sort sub name has been restored.  [perl
           #123410] <https://rt.perl.org/Ticket/Display.html?id=123410>.

       o   Outside of "use utf8", a single-character Latin-1 lexical variable
           is disallowed.  The error message for it, "Can't use global
           $foo...", was giving garbage instead of the variable name.

       o   "readline" on a nonexistent handle was causing "${^LAST_FH}" to
           produce a reference to an undefined scalar (or fail an assertion).
           Now "${^LAST_FH}" ends up undefined.

       o   "(...) x ..." in void context now applies scalar context to the
           left-hand argument, instead of the context the current sub was
           called in.  [perl #123020]
           <https://rt.perl.org/Ticket/Display.html?id=123020>.


Known Problems

       o   "pack"-ing a NaN on a perl compiled with Visual C 6 does not behave
           properly, leading to a test failure in t/op/infnan.t.  [perl
           125203] <https://rt.perl.org/Ticket/Display.html?id=125203>

       o   A goal is for Perl to be able to be recompiled to work reasonably
           well on any Unicode version.  In Perl 5.22, though, the earliest
           such version is Unicode 5.1 (current is 7.0).

       o   EBCDIC platforms

           o   The "cmp" (and hence "sort") operators do not necessarily give
               the correct results when both operands are UTF-EBCDIC encoded
               strings and there is a mixture of ASCII and/or control
               characters, along with other characters.

           o   Ranges containing "\N{...}" in the "tr///" (and "y///")
               transliteration operators are treated differently than the
               equivalent ranges in regular expression patterns.  They should,
               but don't, cause the values in the ranges to all be treated as
               Unicode code points, and not native ones.  ("Version 8 Regular
               Expressions" in perlre gives details as to how it should work.)

           o   Encode and encoding are mostly broken.

           o   Many CPAN modules that are shipped with core show failing
               tests.

           o   "pack"/"unpack" with "U0" format may not work properly.

       o   The following modules are known to have test failures with this
           version of Perl.  In many cases, patches have been submitted, so
           there will hopefully be new releases soon:

           o   B::Generate version 1.50

           o   B::Utils version 0.25

           o   Coro version 6.42

           o   Dancer version 1.3130

           o   Data::Alias version 1.18

           o   Data::Dump::Streamer version 2.38

           o   Data::Util version 0.63

           o   Devel::Spy version 0.07

           o   invoker version 0.34

           o   Lexical::Var version 0.009

           o   LWP::ConsoleLogger version 0.000018

           o   Mason version 2.22

           o   NgxQueue version 0.02

           o   Padre version 1.00

           o   Parse::Keyword 0.08


Obituary

       Brian McCauley died on May 8, 2015.  He was a frequent poster to
       Usenet, Perl Monks, and other Perl forums, and made several CPAN
       contributions under the nick NOBULL, including to the Perl FAQ.  He
       attended almost every YAPC::Europe, and indeed, helped organise
       YAPC::Europe 2006 and the QA Hackathon 2009.  His wit and his delight
       in intricate systems were particularly apparent in his love of board
       games; many Perl mongers will have fond memories of playing Fluxx and
       other games with Brian.  He will be missed.


Acknowledgements

       Perl 5.22.0 represents approximately 12 months of development since
       Perl 5.20.0 and contains approximately 590,000 lines of changes across
       2,400 files from 94 authors.

       Excluding auto-generated files, documentation and release tools, there
       were approximately 370,000 lines of changes to 1,500 .pm, .t, .c and .h
       files.

       Perl continues to flourish into its third decade thanks to a vibrant
       community of users and developers. The following people are known to
       have contributed the improvements that became Perl 5.22.0:

       Aaron Crane, Abhijit Menon-Sen, Abigail, Alberto Simo~es, Alex Solovey,
       Alex Vandiver, Alexandr Ciornii, Alexandre (Midnite) Jousset, Andreas
       Koenig, Andreas Voegele, Andrew Fresh, Andy Dougherty, Anthony Heading,
       Aristotle Pagaltzis, brian d foy, Brian Fraser, Chad Granum, Chris
       'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsaaker, Daniel
       Dragan, Darin McBride, Dave Rolsky, David Golden, David Mitchell, David
       Wheeler, Dmitri Tikhonov, Doug Bell, E. Choroba, Ed J, Eric Herman,
       Father Chrysostomos, George Greer, Glenn D. Golden, Graham Knop,
       H.Merijn Brand, Herbert Breunung, Hugo van der Sanden, James E Keenan,
       James McCoy, James Raspass, Jan Dubois, Jarkko Hietaniemi, Jasmine
       Ngan, Jerry D. Hedden, Jim Cromie, John Goodyear, kafka, Karen
       Etheridge, Karl Williamson, Kent Fredric, kmx, Lajos Veres, Leon
       Timmermans, Lukas Mai, Mathieu Arnold, Matthew Horsfall, Max Maischein,
       Michael Bunk, Nicholas Clark, Niels Thykier, Niko Tyni, Norman Koch,
       Olivier Mengue, Peter John Acklam, Peter Martini, Petr PisaX, Philippe
       Bruhat (BooK), Pierre Bogossian, Rafael Garcia-Suarez, Randy Stauner,
       Reini Urban, Ricardo Signes, Rob Hoelz, Rostislav Skudnov, Sawyer X,
       Shirakata Kentaro, Shlomi Fish, Sisyphus, Slaven Rezic, Smylers,
       Steffen Mueller, Steve Hay, Sullivan Beck, syber, Tadeusz SoXnierz,
       Thomas Sibley, Todd Rinaldo, Tony Cook, Vincent Pit, Vladimir Marek,
       Yaroslav Kuzmin, Yves Orton, AEvar Arnfjoer` Bjarmason.

       The list above is almost certainly incomplete as it is automatically
       generated from version control history. In particular, it does not
       include the names of the (very much appreciated) contributors who
       reported issues to the Perl bug tracker.

       Many of the changes included in this version originated in the CPAN
       modules included in Perl's core. We're grateful to the entire CPAN
       community for helping Perl to flourish.

       For a more complete list of all of Perl's historical contributors,
       please see the AUTHORS file in the Perl source distribution.


Reporting Bugs

       If you find what you think is a bug, you might check the articles
       recently posted to the comp.lang.perl.misc newsgroup and the perl bug
       database at <https://rt.perl.org/>.  There may also be information at
       <http://www.perl.org/>, the Perl Home Page.

       If you believe you have an unreported bug, please run the perlbug
       program included with your release.  Be sure to trim your bug down to a
       tiny but sufficient test case.  Your bug report, along with the output
       of "perl -V", will be sent off to perlbug@perl.org to be analysed by
       the Perl porting team.

       If the bug you are reporting has security implications, which make it
       inappropriate to send to a publicly archived mailing list, then please
       send it to perl5-security-report@perl.org.  This points to a closed
       subscription unarchived mailing list, which includes all the core
       committers, who will be able to help assess the impact of issues,
       figure out a resolution, and help co-ordinate the release of patches to
       mitigate or fix the problem across all platforms on which Perl is
       supported.  Please only use this address for security issues in the
       Perl core, not for modules independently distributed on CPAN.


SEE ALSO

       The Changes file for an explanation of how to view exhaustive details
       on what changed.

       The INSTALL file for how to build Perl.

       The README file for general stuff.

       The Artistic and Copying files for copyright information.



perl v5.24.0                      2016-03-01                PERL5220DELTA(1pm)

perl 5.24 - Generated Sun Nov 27 09:53:56 CST 2016
© manpagez.com 2000-2017
Individual documents may contain additional copyright information.