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PERL581DELTA(1pm)      Perl Programmers Reference Guide      PERL581DELTA(1pm)


       perl581delta - what is new for perl v5.8.1


       This document describes differences between the 5.8.0 release and the
       5.8.1 release.

       If you are upgrading from an earlier release such as 5.6.1, first read
       the perl58delta, which describes differences between 5.6.0 and 5.8.0.

       In case you are wondering about 5.6.1, it was bug-fix-wise rather
       identical to the development release 5.7.1.  Confused?  This timeline
       hopefully helps a bit: it lists the new major releases, their
       maintenance releases, and the development releases.

                 New     Maintenance  Development

                 5.6.0                             2000-Mar-22
                                      5.7.0        2000-Sep-02
                         5.6.1                     2001-Apr-08
                                      5.7.1        2001-Apr-09
                                      5.7.2        2001-Jul-13
                                      5.7.3        2002-Mar-05
                 5.8.0                             2002-Jul-18
                         5.8.1                     2003-Sep-25

Incompatible Changes

   Hash Randomisation
       Mainly due to security reasons, the "random ordering" of hashes has
       been made even more random.  Previously while the order of hash
       elements from keys(), values(), and each() was essentially random, it
       was still repeatable.  Now, however, the order varies between different
       runs of Perl.

       Perl has never guaranteed any ordering of the hash keys, and the
       ordering has already changed several times during the lifetime of Perl
       5.  Also, the ordering of hash keys has always been, and continues to
       be, affected by the insertion order.

       The added randomness may affect applications.

       One possible scenario is when output of an application has included
       hash data.  For example, if you have used the Data::Dumper module to
       dump data into different files, and then compared the files to see
       whether the data has changed, now you will have false positives since
       the order in which hashes are dumped will vary.  In general the cure is
       to sort the keys (or the values); in particular for Data::Dumper to use
       the "Sortkeys" option.  If some particular order is really important,
       use tied hashes: for example the Tie::IxHash module which by default
       preserves the order in which the hash elements were added.

       More subtle problem is reliance on the order of "global destruction".
       That is what happens at the end of execution: Perl destroys all data
       structures, including user data.  If your destructors (the DESTROY
       subroutines) have assumed any particular ordering to the global
       destruction, there might be problems ahead.  For example, in a
       destructor of one object you cannot assume that objects of any other
       class are still available, unless you hold a reference to them.  If the
       environment variable PERL_DESTRUCT_LEVEL is set to a non-zero value, or
       if Perl is exiting a spawned thread, it will also destruct the ordinary
       references and the symbol tables that are no longer in use.  You can't
       call a class method or an ordinary function on a class that has been
       collected that way.

       The hash randomisation is certain to reveal hidden assumptions about
       some particular ordering of hash elements, and outright bugs: it
       revealed a few bugs in the Perl core and core modules.

       To disable the hash randomisation in runtime, set the environment
       variable PERL_HASH_SEED to 0 (zero) before running Perl (for more
       information see "PERL_HASH_SEED" in perlrun), or to disable the feature
       completely in compile time, compile with "-DNO_HASH_SEED" (see

       See "Algorithmic Complexity Attacks" in perlsec for the original
       rationale behind this change.

   UTF-8 On Filehandles No Longer Activated By Locale
       In Perl 5.8.0 all filehandles, including the standard filehandles, were
       implicitly set to be in Unicode UTF-8 if the locale settings indicated
       the use of UTF-8.  This feature caused too many problems, so the
       feature was turned off and redesigned: see "Core Enhancements".

   Single-number v-strings are no longer v-strings before "=>"
       The version strings or v-strings (see "Version Strings" in perldata)
       feature introduced in Perl 5.6.0 has been a source of some confusion--
       especially when the user did not want to use it, but Perl thought it
       knew better.  Especially troublesome has been the feature that before a
       "=>" a version string (a "v" followed by digits) has been interpreted
       as a v-string instead of a string literal.  In other words:

               %h = ( v65 => 42 );

       has meant since Perl 5.6.0

               %h = ( 'A' => 42 );

       (at least in platforms of ASCII progeny)  Perl 5.8.1 restores the more
       natural interpretation

               %h = ( 'v65' => 42 );

       The multi-number v-strings like v65.66 and 65.66.67 still continue to
       be v-strings in Perl 5.8.

   (Win32) The -C Switch Has Been Repurposed
       The -C switch has changed in an incompatible way.  The old semantics of
       this switch only made sense in Win32 and only in the "use utf8"
       universe in 5.6.x releases, and do not make sense for the Unicode
       implementation in 5.8.0.  Since this switch could not have been used by
       anyone, it has been repurposed.  The behavior that this switch enabled
       in 5.6.x releases may be supported in a transparent, data-dependent
       fashion in a future release.

       For the new life of this switch, see "UTF-8 no longer default under
       UTF-8 locales", and "-C" in perlrun.

   (Win32) The /d Switch Of cmd.exe
       Perl 5.8.1 uses the /d switch when running the cmd.exe shell internally
       for system(), backticks, and when opening pipes to external programs.
       The extra switch disables the execution of AutoRun commands from the
       registry, which is generally considered undesirable when running
       external programs.  If you wish to retain compatibility with the older
       behavior, set PERL5SHELL in your environment to "cmd /x/c".

Core Enhancements

   UTF-8 no longer default under UTF-8 locales
       In Perl 5.8.0 many Unicode features were introduced.   One of them was
       found to be of more nuisance than benefit: the automagic (and silent)
       "UTF-8-ification" of filehandles, including the standard filehandles,
       if the user's locale settings indicated use of UTF-8.

       For example, if you had "en_US.UTF-8" as your locale, your STDIN and
       STDOUT were automatically "UTF-8", in other words an implicit
       binmode(..., ":utf8") was made.  This meant that trying to print, say,
       chr(0xff), ended up printing the bytes 0xc3 0xbf.  Hardly what you had
       in mind unless you were aware of this feature of Perl 5.8.0.  The
       problem is that the vast majority of people weren't: for example in
       RedHat releases 8 and 9 the default locale setting is UTF-8, so all
       RedHat users got UTF-8 filehandles, whether they wanted it or not.  The
       pain was intensified by the Unicode implementation of Perl 5.8.0
       (still) having nasty bugs, especially related to the use of s/// and
       tr///.  (Bugs that have been fixed in 5.8.1)

       Therefore a decision was made to backtrack the feature and change it
       from implicit silent default to explicit conscious option.  The new
       Perl command line option "-C" and its counterpart environment variable
       PERL_UNICODE can now be used to control how Perl and Unicode interact
       at interfaces like I/O and for example the command line arguments.  See
       "-C" in perlrun and "PERL_UNICODE" in perlrun for more information.

   Unsafe signals again available
       In Perl 5.8.0 the so-called "safe signals" were introduced.  This means
       that Perl no longer handles signals immediately but instead "between
       opcodes", when it is safe to do so.  The earlier immediate handling
       easily could corrupt the internal state of Perl, resulting in
       mysterious crashes.

       However, the new safer model has its problems too.  Because now an
       opcode, a basic unit of Perl execution, is never interrupted but
       instead let to run to completion, certain operations that can take a
       long time now really do take a long time.  For example, certain network
       operations have their own blocking and timeout mechanisms, and being
       able to interrupt them immediately would be nice.

       Therefore perl 5.8.1 introduces a "backdoor" to restore the pre-5.8.0
       (pre-5.7.3, really) signal behaviour.  Just set the environment
       variable PERL_SIGNALS to "unsafe", and the old immediate (and unsafe)
       signal handling behaviour returns.  See "PERL_SIGNALS" in perlrun and
       "Deferred Signals (Safe Signals)" in perlipc.

       In completely unrelated news, you can now use safe signals with
       POSIX::SigAction.  See "POSIX::SigAction" in POSIX.

   Tied Arrays with Negative Array Indices
       Formerly, the indices passed to "FETCH", "STORE", "EXISTS", and
       "DELETE" methods in tied array class were always non-negative.  If the
       actual argument was negative, Perl would call FETCHSIZE implicitly and
       add the result to the index before passing the result to the tied array
       method.  This behaviour is now optional.  If the tied array class
       contains a package variable named $NEGATIVE_INDICES which is set to a
       true value, negative values will be passed to "FETCH", "STORE",
       "EXISTS", and "DELETE" unchanged.

   local ${$x}
       The syntaxes

               local ${$x}
               local @{$x}
               local %{$x}

       now do localise variables, given that the $x is a valid variable name.

   Unicode Character Database 4.0.0
       The copy of the Unicode Character Database included in Perl 5.8 has
       been updated to 4.0.0 from 3.2.0.  This means for example that the
       Unicode character properties are as in Unicode 4.0.0.

   Deprecation Warnings
       There is one new feature deprecation.  Perl 5.8.0 forgot to add some
       deprecation warnings, these warnings have now been added.  Finally, a
       reminder of an impending feature removal.

       (Reminder) Pseudo-hashes are deprecated (really)

       Pseudo-hashes were deprecated in Perl 5.8.0 and will be removed in Perl
       5.10.0, see perl58delta for details.  Each attempt to access pseudo-
       hashes will trigger the warning "Pseudo-hashes are deprecated".  If you
       really want to continue using pseudo-hashes but not to see the
       deprecation warnings, use:

           no warnings 'deprecated';

       Or you can continue to use the fields pragma, but please don't expect
       the data structures to be pseudohashes any more.

       (Reminder) 5.005-style threads are deprecated (really)

       5.005-style threads (activated by "use Thread;") were deprecated in
       Perl 5.8.0 and will be removed after Perl 5.8, see perl58delta for
       details.  Each 5.005-style thread creation will trigger the warning
       "5.005 threads are deprecated".  If you really want to continue using
       the 5.005 threads but not to see the deprecation warnings, use:

           no warnings 'deprecated';

       (Reminder) The $* variable is deprecated (really)

       The $* variable controlling multi-line matching has been deprecated and
       will be removed after 5.8.  The variable has been deprecated for a long
       time, and a deprecation warning "Use of $* is deprecated" is given, now
       the variable will just finally be removed.  The functionality has been
       supplanted by the "/s" and "/m" modifiers on pattern matching.  If you
       really want to continue using the $*-variable but not to see the
       deprecation warnings, use:

           no warnings 'deprecated';

   Miscellaneous Enhancements
       "map" in void context is no longer expensive. "map" is now context
       aware, and will not construct a list if called in void context.

       If a socket gets closed by the server while printing to it, the client
       now gets a SIGPIPE.  While this new feature was not planned, it fell
       naturally out of PerlIO changes, and is to be considered an accidental

       PerlIO::get_layers(FH) returns the names of the PerlIO layers active on
       a filehandle.

       PerlIO::via layers can now have an optional UTF8 method to indicate
       whether the layer wants to "auto-:utf8" the stream.

       utf8::is_utf8() has been added as a quick way to test whether a scalar
       is encoded internally in UTF-8 (Unicode).

Modules and Pragmata

   Updated Modules And Pragmata
       The following modules and pragmata have been updated since Perl 5.8.0:

           In much better shape than it used to be.  Still far from perfect,
           but maybe worth a try.

           An optional feature, ":hireswallclock", now allows for high
           resolution wall clock times (uses Time::HiRes).

           See B::Bytecode.

           Now has bytes::substr.

           One can now have custom character name aliases.

           There is now a simple command line frontend to the module
           called cpan.

           A new option, Pair, allows choosing the separator between hash keys
           and values.

           Significant updates on the encoding pragma functionality (tr/// and
           the DATA filehandle, formats).

           If a filehandle has been marked as to have an encoding, unmappable
           characters are detected already during input, not later (when the
           corrupted data is being used).

           The ISO 8859-6 conversion table has been corrected (the 0x30..0x39
           erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039).
           The GSM 03.38 conversion did not handle escape sequences correctly.
           The UTF-7 encoding has been added (making Encode feature-complete
           with Unicode::String).

           A lot of bugs have been fixed since v1.60, the version included in
           Perl v5.8.0. Especially noteworthy are the bug in Calc that caused
           div and mod to fail for some large values, and the fixes to the
           handling of bad inputs.

           Some new features were added, e.g. the broot() method, you can now
           pass parameters to config() to change some settings at runtime, and
           it is now possible to trap the creation of NaN and infinity.

           As usual, some optimizations took place and made the math overall a
           tad faster. In some cases, quite a lot faster, actually. Especially
           alternative libraries like Math::BigInt::GMP benefit from this. In
           addition, a lot of the quite clunky routines like fsqrt() and
           flog() are now much much faster.

           Diamond inheritance now works.

           Reading from non-string scalars (like the special variables, see
           perlvar) now works.

           Complete rewrite.  As a side-effect, no longer refuses to startup
           when run by root.

           New utilities: refaddr, isvstring, looks_like_number,

           Can now store code references (via B::Deparse, so not foolproof).

           Earlier versions of the strict pragma did not check the parameters
           implicitly passed to its "import" (use) and "unimport" (no)
           routine.  This caused the false idiom such as:

                   use strict qw(@ISA);
                   @ISA = qw(Foo);

           This however (probably) raised the false expectation that the
           strict refs, vars and subs were being enforced (and that @ISA was
           somehow "declared").  But the strict refs, vars, and subs are not
           enforced when using this false idiom.

           Starting from Perl 5.8.1, the above will cause an error to be
           raised.  This may cause programs which used to execute seemingly
           correctly without warnings and errors to fail when run under 5.8.1.
           This happens because

                   use strict qw(@ISA);

           will now fail with the error:

                   Unknown 'strict' tag(s) '@ISA'

           The remedy to this problem is to replace this code with the correct

                   use strict;
                   use vars qw(@ISA);
                   @ISA = qw(Foo);

           Now much more picky about extra or missing output from test

           Use of nanosleep(), if available, allows mixing subsecond sleeps
           with alarms.

           Several fixes, for example for join() problems and memory leaks.
           In some platforms (like Linux) that use glibc the minimum memory
           footprint of one ithread has been reduced by several hundred

           Many memory leaks have been fixed.

           Now returns extra information.

Utility Changes

       The "h2xs" utility now produces a more modern layout:
       Foo-Bar/lib/Foo/ instead of Foo/Bar/  Also, the
       boilerplate test is now called t/Foo-Bar.t instead of t/1.t.

       The Perl debugger (lib/ has now been extensively documented
       and bugs found while documenting have been fixed.

       "perldoc" has been rewritten from scratch to be more robust and feature

       "perlcc -B" works now at least somewhat better, while "perlcc -c" is
       rather more broken.  (The Perl compiler suite as a whole continues to
       be experimental.)

New Documentation

       perl573delta has been added to list the differences between the (now
       quite obsolete) development releases 5.7.2 and 5.7.3.

       perl58delta has been added: it is the perldelta of 5.8.0, detailing the
       differences between 5.6.0 and 5.8.0.

       perlartistic has been added: it is the Artistic License in pod format,
       making it easier for modules to refer to it.

       perlcheat has been added: it is a Perl cheat sheet.

       perlgpl has been added: it is the GNU General Public License in pod
       format, making it easier for modules to refer to it.

       perlmacosx has been added to tell about the installation and use of
       Perl in Mac OS X.

       perlos400 has been added to tell about the installation and use of Perl
       in OS/400 PASE.

       perlreref has been added: it is a regular expressions quick reference.

Installation and Configuration Improvements

       The Unix standard Perl location, /usr/bin/perl, is no longer
       overwritten by default if it exists.  This change was very prudent
       because so many Unix vendors already provide a /usr/bin/perl, but
       simultaneously many system utilities may depend on that exact version
       of Perl, so better not to overwrite it.

       One can now specify installation directories for site and vendor man
       and HTML pages, and site and vendor scripts.  See INSTALL.

       One can now specify a destination directory for Perl installation by
       specifying the DESTDIR variable for "make install".  (This feature is
       slightly different from the previous "Configure -Dinstallprefix=...".)
       See INSTALL.

       gcc versions 3.x introduced a new warning that caused a lot of noise
       during Perl compilation: "gcc -Ialreadyknowndirectory (warning:
       changing search order)".  This warning has now been avoided by
       Configure weeding out such directories before the compilation.

       One can now build subsets of Perl core modules by using the Configure
       flags "-Dnoextensions=..." and "-Donlyextensions=...", see INSTALL.

   Platform-specific enhancements
       In Cygwin Perl can now be built with threads ("Configure
       -Duseithreads").  This works with both Cygwin 1.3.22 and Cygwin 1.5.3.

       In newer FreeBSD releases Perl 5.8.0 compilation failed because of
       trying to use malloc.h, which in FreeBSD is just a dummy file, and a
       fatal error to even try to use.  Now malloc.h is not used.

       Perl is now known to build also in Hitachi HI-UXMPP.

       Perl is now known to build again in LynxOS.

       Mac OS X now installs with Perl version number embedded in installation
       directory names for easier upgrading of user-compiled Perl, and the
       installation directories in general are more standard.  In other words,
       the default installation no longer breaks the Apple-provided Perl.  On
       the other hand, with "Configure -Dprefix=/usr" you can now really
       replace the Apple-supplied Perl (please be careful).

       Mac OS X now builds Perl statically by default.  This change was done
       mainly for faster startup times.  The Apple-provided Perl is still
       dynamically linked and shared, and you can enable the sharedness for
       your own Perl builds by "Configure -Duseshrplib".

       Perl has been ported to IBM's OS/400 PASE environment.  The best way to
       build a Perl for PASE is to use an AIX host as a cross-compilation
       environment.  See README.os400.

       Yet another cross-compilation option has been added: now Perl builds on
       OpenZaurus, an Linux distribution based on Mandrake + Embedix for the
       Sharp Zaurus PDA.  See the Cross/README file.

       Tru64 when using gcc 3 drops the optimisation for toke.c to "-O2"
       because of gigantic memory use with the default "-O3".

       Tru64 can now build Perl with the newer Berkeley DBs.

       Building Perl on WinCE has been much enhanced, see README.ce and

Selected Bug Fixes

   Closures, eval and lexicals
       There have been many fixes in the area of anonymous subs, lexicals and
       closures.  Although this means that Perl is now more "correct", it is
       possible that some existing code will break that happens to rely on the
       faulty behaviour.  In practice this is unlikely unless your code
       contains a very complex nesting of anonymous subs, evals and lexicals.

   Generic fixes
       If an input filehandle is marked ":utf8" and Perl sees illegal UTF-8
       coming in when doing "<FH>", if warnings are enabled a warning is
       immediately given - instead of being silent about it and Perl being
       unhappy about the broken data later.  (The ":encoding(utf8)" layer also
       works the same way.)

       binmode(SOCKET, ":utf8") only worked on the input side, not on the
       output side of the socket.  Now it works both ways.

       For threaded Perls certain system database functions like getpwent()
       and getgrent() now grow their result buffer dynamically, instead of
       failing.  This means that at sites with lots of users and groups the
       functions no longer fail by returning only partial results.

       Perl 5.8.0 had accidentally broken the capability for users to define
       their own uppercase<->lowercase Unicode mappings (as advertised by the
       Camel).  This feature has been fixed and is also documented better.

       In 5.8.0 this

               $some_unicode .= <FH>;

       didn't work correctly but instead corrupted the data.  This has now
       been fixed.

       Tied methods like FETCH etc. may now safely access tied values, i.e.
       resulting in a recursive call to FETCH etc.  Remember to break the
       recursion, though.

       At startup Perl blocks the SIGFPE signal away since there isn't much
       Perl can do about it.  Previously this blocking was in effect also for
       programs executed from within Perl.  Now Perl restores the original
       SIGFPE handling routine, whatever it was, before running external

       Linenumbers in Perl scripts may now be greater than 65536, or 2**16.
       (Perl scripts have always been able to be larger than that, it's just
       that the linenumber for reported errors and warnings have "wrapped
       around".)  While scripts that large usually indicate a need to rethink
       your code a bit, such Perl scripts do exist, for example as results
       from generated code.  Now linenumbers can go all the way to 4294967296,
       or 2**32.

   Platform-specific fixes

       o   Setting $0 works again (with certain limitations that Perl cannot
           do much about: see "$0" in perlvar)


       o   Setting $0 now works.


       o   Configuration now tests for the presence of "poll()", and IO::Poll
           now uses the vendor-supplied function if detected.

       o   A rare access violation at Perl start-up could occur if the Perl
           image was installed with privileges or if there was an identifier
           with the subsystem attribute set in the process's rightslist.
           Either of these circumstances triggered tainting code that
           contained a pointer bug.  The faulty pointer arithmetic has been

       o   The length limit on values (not keys) in the %ENV hash has been
           raised from 255 bytes to 32640 bytes (except when the
           PERL_ENV_TABLES setting overrides the default use of logical names
           for %ENV).  If it is necessary to access these long values from
           outside Perl, be aware that they are implemented using search list
           logical names that store the value in pieces, each 255-byte piece
           (up to 128 of them) being an element in the search list. When doing
           a lookup in %ENV from within Perl, the elements are combined into a
           single value.  The existing VMS-specific ability to access
           individual elements of a search list logical name via the
           $ENV{'foo;N'} syntax (where N is the search list index) is

       o   The piping implementation now uses local rather than global DCL
           symbols for inter-process communication.

       o   File::Find could become confused when navigating to a relative
           directory whose name collided with a logical name.  This problem
           has been corrected by adding directory syntax to relative path
           names, thus preventing logical name translation.


       o   A memory leak in the fork() emulation has been fixed.

       o   The return value of the ioctl() built-in function was accidentally
           broken in 5.8.0.  This has been corrected.

       o   The internal message loop executed by perl during blocking
           operations sometimes interfered with messages that were external to
           Perl.  This often resulted in blocking operations terminating
           prematurely or returning incorrect results, when Perl was executing
           under environments that could generate Windows messages.  This has
           been corrected.

       o   Pipes and sockets are now automatically in binary mode.

       o   The four-argument form of select() did not preserve $! (errno)
           properly when there were errors in the underlying call.  This is
           now fixed.

       o   The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf") is
           now effectively a no-op.

New or Changed Diagnostics

       All the warnings related to pack() and unpack() were made more
       informative and consistent.

   Changed "A thread exited while %d threads were running"
       The old version

           A thread exited while %d other threads were still running

       was misleading because the "other" included also the thread giving the

   Removed "Attempt to clear a restricted hash"
       It is not illegal to clear a restricted hash, so the warning was

   New "Illegal declaration of anonymous subroutine"
       You must specify the block of code for "sub".

   Changed "Invalid range "%s" in transliteration operator"
       The old version

           Invalid [] range "%s" in transliteration operator

       was simply wrong because there are no "[] ranges" in tr///.

   New "Missing control char name in \c"

   New "Newline in left-justified string for %s"
       The padding spaces would appear after the newline, which is probably
       not what you had in mind.

   New "Possible precedence problem on bitwise %c operator"
       If you think this

           $x & $y == 0

       tests whether the bitwise AND of $x and $y is zero, you will like this

   New "Pseudo-hashes are deprecated"
       This warning should have been already in 5.8.0, since they are.

   New "read() on %s filehandle %s"
       You cannot read() (or sysread()) from a closed or unopened filehandle.

   New "5.005 threads are deprecated"
       This warning should have been already in 5.8.0, since they are.

   New "Tied variable freed while still in use"
       Something pulled the plug on a live tied variable, Perl plays safe by
       bailing out.

   New "To%s: illegal mapping '%s'"
       An illegal user-defined Unicode casemapping was specified.

   New "Use of freed value in iteration"
       Something modified the values being iterated over.  This is not good.

Changed Internals

       These news matter to you only if you either write XS code or like to
       know about or hack Perl internals (using Devel::Peek or any of the
       "B::" modules counts), or like to run Perl with the "-D" option.

       The embedding examples of perlembed have been reviewed to be up to date
       and consistent: for example, the correct use of PERL_SYS_INIT3() and

       Extensive reworking of the pad code (the code responsible for lexical
       variables) has been conducted by Dave Mitchell.

       Extensive work on the v-strings by John Peacock.

       UTF-8 length and position cache: to speed up the handling of Unicode
       (UTF-8) scalars, a cache was introduced.  Potential problems exist if
       an extension bypasses the official APIs and directly modifies the PV of
       an SV: the UTF-8 cache does not get cleared as it should.

       APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv,
       sv_setsv, are again available.

       Certain Perl core C APIs like cxinc and regatom are no longer available
       at all to code outside the Perl core of the Perl core extensions.  This
       is intentional.  They never should have been available with the shorter
       names, and if you application depends on them, you should (be ashamed
       and) contact perl5-porters to discuss what are the proper APIs.

       Certain Perl core C APIs like "Perl_list" are no longer available
       without their "Perl_" prefix.  If your XS module stops working because
       some functions cannot be found, in many cases a simple fix is to add
       the "Perl_" prefix to the function and the thread context "aTHX_" as
       the first argument of the function call.  This is also how it should
       always have been done: letting the Perl_-less forms to leak from the
       core was an accident.  For cleaner embedding you can also force this
       for all APIs by defining at compile time the cpp define

       Perl_save_bool() has been added.

       Regexp objects (those created with "qr") now have S-magic rather than
       R-magic.  This fixed regexps of the form /...(??{...;$x})/ to no longer
       ignore changes made to $x.  The S-magic avoids dropping the caching
       optimization and making (??{...}) constructs obscenely slow (and
       consequently useless).  See also "Magic Variables" in perlguts.
       Regexp::Copy was affected by this change.

       The Perl internal debugging macros DEBUG() and DEB() have been renamed
       to PERL_DEBUG() and PERL_DEB() to avoid namespace conflicts.

       "-DL" removed (the leaktest had been broken and unsupported for years,
       use alternative debugging mallocs or tools like valgrind and Purify).

       Verbose modifier "v" added for "-DXv" and "-Dsv", see perlrun.

New Tests

       In Perl 5.8.0 there were about 69000 separate tests in about 700 test
       files, in Perl 5.8.1 there are about 77000 separate tests in about 780
       test files.  The exact numbers depend on the Perl configuration and on
       the operating system platform.

Known Problems

       The hash randomisation mentioned in "Incompatible Changes" is
       definitely problematic: it will wake dormant bugs and shake out bad

       If you want to use mod_perl 2.x with Perl 5.8.1, you will need
       mod_perl-1.99_10 or higher.  Earlier versions of mod_perl 2.x do not
       work with the randomised hashes.  (mod_perl 1.x works fine.)  You will
       also need Apache::Test 1.04 or higher.

       Many of the rarer platforms that worked 100% or pretty close to it with
       perl 5.8.0 have been left a little bit untended since their maintainers
       have been otherwise busy lately, and therefore there will be more
       failures on those platforms.  Such platforms include Mac OS Classic,
       IBM z/OS (and other EBCDIC platforms), and NetWare.  The most common
       Perl platforms (Unix and Unix-like, Microsoft platforms, and VMS) have
       large enough testing and expert population that they are doing well.

   Tied hashes in scalar context
       Tied hashes do not currently return anything useful in scalar context,
       for example when used as boolean tests:

               if (%tied_hash) { ... }

       The current nonsensical behaviour is always to return false, regardless
       of whether the hash is empty or has elements.

       The root cause is that there is no interface for the implementors of
       tied hashes to implement the behaviour of a hash in scalar context.

   Net::Ping 450_service and 510_ping_udp failures
       The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the subtest
       2 of lib/Net/Ping/t/510_ping_udp.t might fail if you have an unusual
       networking setup.  For example in the latter case the test is trying to
       send a UDP ping to the IP address

       The C-generating compiler backend B::C (the frontend being "perlcc -c")
       is even more broken than it used to be because of the extensive lexical
       variable changes.  (The good news is that B::Bytecode and ByteLoader
       are better than they used to be.)

Platform Specific Problems

   EBCDIC Platforms
       IBM z/OS and other EBCDIC platforms continue to be problematic
       regarding Unicode support.  Many Unicode tests are skipped when they
       really should be fixed.

   Cygwin 1.5 problems
       In Cygwin 1.5 the io/tell and op/sysio tests have failures for some yet
       unknown reason.  In 1.5.5 the threads tests stress_cv, stress_re, and
       stress_string are failing unless the environment variable PERLIO is set
       to "perlio" (which makes also the io/tell failure go away).

       Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a)
       "CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ..."  a 100%
       "make test"  was achieved with "Configure -des -Duseithreads".

   HP-UX: HP cc warnings about sendfile and sendpath
       With certain HP C compiler releases (e.g. B.11.11.02) you will get many
       warnings like this (lines wrapped for easier reading):

         cc: "/usr/include/sys/socket.h", line 504: warning 562:
           Redeclaration of "sendfile" with a different storage class specifier:
             "sendfile" will have internal linkage.
         cc: "/usr/include/sys/socket.h", line 505: warning 562:
           Redeclaration of "sendpath" with a different storage class specifier:
             "sendpath" will have internal linkage.

       The warnings show up both during the build of Perl and during certain
       lib/ExtUtils tests that invoke the C compiler.  The warning, however,
       is not serious and can be ignored.

   IRIX: t/uni/tr_7jis.t falsely failing
       The test t/uni/tr_7jis.t is known to report failure under 'make test'
       or the test harness with certain releases of IRIX (at least IRIX 6.5
       and MIPSpro Compilers Version, but if run manually the test
       fully passes.

   Mac OS X: no usemymalloc
       The Perl malloc ("-Dusemymalloc") does not work at all in Mac OS X.
       This is not that serious, though, since the native malloc works just

   Tru64: No threaded builds with GNU cc (gcc)
       In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used
       to compile a threaded Perl (-Duseithreads) because the system
       "<pthread.h>" file doesn't know about gcc.

   Win32: sysopen, sysread, syswrite
       As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave
       like they used to in 5.6.1 and earlier with respect to "text" mode.
       These built-ins now always operate in "binary" mode (even if sysopen()
       was passed the O_TEXT flag, or if binmode() was used on the file
       handle).  Note that this issue should only make a difference for disk
       files, as sockets and pipes have always been in "binary" mode in the
       Windows port.  As this behavior is currently considered a bug,
       compatible behavior may be re-introduced in a future release.  Until
       then, the use of sysopen(), sysread() and syswrite() is not supported
       for "text" mode operations.

Future Directions

       The following things might happen in future.  The first publicly
       available releases having these characteristics will be the developer
       releases Perl 5.9.x, culminating in the Perl 5.10.0 release.  These are
       our best guesses at the moment: we reserve the right to rethink.

       o   PerlIO will become The Default.  Currently (in Perl 5.8.x) the
           stdio library is still used if Perl thinks it can use certain
           tricks to make stdio go really fast.  For future releases our goal
           is to make PerlIO go even faster.

       o   A new feature called assertions will be available.  This means that
           one can have code called assertions sprinkled in the code: usually
           they are optimised away, but they can be enabled with the "-A"

       o   A new operator "//" (defined-or) will be available.  This means
           that one will be able to say

               $a // $b

           instead of

              defined $a ? $a : $b


              $c //= $d;

           instead of

              $c = $d unless defined $c;

           The operator will have the same precedence and associativity as
           "||".  A source code patch against the Perl 5.8.1 sources will be
           available in CPAN as authors/id/H/HM/HMBRAND/dor-5.8.1.diff.

       o   "unpack()" will default to unpacking the $_.

       o   Various Copy-On-Write techniques will be investigated in hopes of
           speeding up Perl.

       o   CPANPLUS, Inline, and Module::Build will become core modules.

       o   The ability to write true lexically scoped pragmas will be

       o   Work will continue on the bytecompiler and byteloader.

       o   v-strings as they currently exist are scheduled to be deprecated.
           The v-less form (1.2.3) will become a "version object" when used
           with "use", "require", and $VERSION.  $^V will also be a "version
           object" so the printf("%vd",...) construct will no longer be
           needed.  The v-ful version (v1.2.3) will become obsolete.  The
           equivalence of strings and v-strings (e.g.  that currently 5.8.0 is
           equal to "\5\8\0") will go away.  There may be no deprecation
           warning for v-strings, though: it is quite hard to detect when
           v-strings are being used safely, and when they are not.

       o   5.005 Threads Will Be Removed

       o   The $* Variable Will Be Removed (it was deprecated a long time ago)

       o   Pseudohashes Will Be Removed

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 .  There may also be information at , 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 to be analysed by
       the Perl porting team.  You can browse and search the Perl 5 bugs at


       The Changes file for 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                      2015-10-14                 PERL581DELTA(1pm)

perl 5.24 - Generated Sun Nov 27 10:24:50 CST 2016
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