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B::Xref(3pm)           Perl Programmers Reference Guide           B::Xref(3pm)


       B::Xref - Generates cross reference reports for Perl programs


       perl -MO=Xref[,OPTIONS]


       The B::Xref module is used to generate a cross reference listing of all
       definitions and uses of variables, subroutines and formats in a Perl
       program.  It is implemented as a backend for the Perl compiler.

       The report generated is in the following format:

           File filename1
             Subroutine subname1
               Package package1
                 object1        line numbers
                 object2        line numbers
               Package package2

       Each File section reports on a single file. Each Subroutine section
       reports on a single subroutine apart from the special cases
       "(definitions)" and "(main)". These report, respectively, on subroutine
       definitions found by the initial symbol table walk and on the main part
       of the program or module external to all subroutines.

       The report is then grouped by the Package of each variable, subroutine
       or format with the special case "(lexicals)" meaning lexical variables.
       Each object name (implicitly qualified by its containing Package)
       includes its type character(s) at the beginning where possible. Lexical
       variables are easier to track and even included dereferencing
       information where possible.

       The "line numbers" are a comma separated list of line numbers (some
       preceded by code letters) where that object is used in some way.
       Simple uses aren't preceded by a code letter. Introductions (such as
       where a lexical is first defined with "my") are indicated with the
       letter "i". Subroutine and method calls are indicated by the character
       "&".  Subroutine definitions are indicated by "s" and format
       definitions by "f".

       For instance, here's part of the report from the pod2man program that
       comes with Perl:

         Subroutine clear_noremap
           Package (lexical)
             $ready_to_print   i1069, 1079
           Package main
             $&                1086
             $.                1086
             $0                1086
             $1                1087
             $2                1085, 1085
             $3                1085, 1085
             $ARGV             1086
             %HTML_Escapes     1085, 1085

       This shows the variables used in the subroutine "clear_noremap".  The
       variable $ready_to_print is a my() (lexical) variable, introduced
       (first declared with my()) on line 1069, and used on line 1079.  The
       variable $& from the main package is used on 1086, and so on.

       A line number may be prefixed by a single letter:

       i   Lexical variable introduced (declared with my()) for the first

       &   Subroutine or method call.

       s   Subroutine defined.

       r   Format defined.

       The most useful option the cross referencer has is to save the report
       to a separate file.  For instance, to save the report on myperlprogram
       to the file report:

         $ perl -MO=Xref,-oreport myperlprogram


       Option words are separated by commas (not whitespace) and follow the
       usual conventions of compiler backend options.

               Directs output to "FILENAME" instead of standard output.

       "-r"    Raw output. Instead of producing a human-readable report,
               outputs a line in machine-readable form for each definition/use
               of a variable/sub/format.

       "-d"    Don't output the "(definitions)" sections.

               (Internal) debug options, probably only useful if "-r"
               included.  The "t" option prints the object on the top of the
               stack as it's being tracked. The "O" option prints each
               operator as it's being processed in the execution order of the


       Non-lexical variables are quite difficult to track through a program.
       Sometimes the type of a non-lexical variable's use is impossible to
       determine. Introductions of non-lexical non-scalars don't seem to be
       reported properly.


       Malcolm Beattie,

perl v5.24.0                      2016-02-05                      B::Xref(3pm)

perl 5.24 - Generated Thu Nov 3 16:06:06 CDT 2016
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