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       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 time.

       &   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,