Symbol(3)

NNAAMMEE
       Apache::Symbol - Things for symbol things

SSYYNNOOPPSSIISS
        use Apache::Symbol ();

        @ISA = qw(Apache::Symbol);

DDEESSCCRRIIPPTTIIOONN
       ppeerrllssuubb//CCoonnssttaanntt FFuunnccttiioonnss says:

        If you redefine a subroutine which was eligible for inlining you'll get
        a mandatory warning.  (You can use this warning to tell whether or not a
        particular subroutine is considered constant.)  The warning is
        considered severe enough not to be optional because previously compiled
        invocations of the function will still be using the old value of the
        function.

       mandatory warning means there is _no_ way to avoid this
       warning no matter what tricks you pull in Perl.  This is
       bogus for us mod_perl users when restarting the server
       with PPeerrllFFrreesshhRReessttaarrtt on or when Apache::StatINC pulls in
       a module that has changed on disk.

       You can, however, pull some tricks with XS to avoid this
       warning, AAppaacchhee::::SSyymmbbooll::::uunnddeeff does just that.

AARRGGUUMMEENNTTSS
       undef_functions takes two arguments: skip and
       only_undef_exports.

       skip is a regular expression indicating the function names
       to skip.

       Use the only_undef_exports flag to undef only those
       functions which are listed in @EXPORT, @EXPORT_OK,
       %EXPORT_TAGS, or @EXPORT_EXTRAS.  @EXPORT_EXTRAS is not
       used by the Exporter, it is only exists to communicate
       with undef_functions.

       As a special case, if none of the EXPORT variables are
       defined ignore only_undef_exports.  This takes care of
       trivial modules that don't use the Exporter.

AARRGGUUMMEENNTTSS
       undef_functions takes two arguments: skip and
       only_undef_exports.

       skip is a regular expression indicating the function names
       to skip.

       Use the only_undef_exports flag to undef only those
       functions which are listed in @EXPORT, @EXPORT_OK,

       %EXPORT_TAGS, or @EXPORT_EXTRAS.  @EXPORT_EXTRAS is not
       used by the Exporter, it is only exists to communicate
       with undef_functions.

       As a special case, if none of the EXPORT variables are
       defined ignore only_undef_exports.  This takes care of
       trivial modules that don't use the Exporter.

PPLLAAYYEERRSS
       This module and the undefining of functions is optional,
       if you wish to have this functionality enabled, there are
       one or more switches you need to know about.

       PerlRestartHandler
           Apache::Symbol defines a PerlRestartHandler which can
           be useful in conjuction with PerlFreshRestart On as it
           will avoid subroutine redefinition messages.
           Configure like so:

            PerlRestartHandler Apache::Symbol

       Apache::Registry
           By placing the SYNOPSIS bit in you script,
           Apache::Registry will undefine subroutines in your
           script before it is re-compiled to avoid "subroutine
           re-defined" warnings.

       Apache::StatINC
           See Apache::StatINC's docs.

       APACHE_SYMBOL_UNIVERSAL
           If this environment variable is true when Symbol.pm is
           compiled, it will define UNIVERSAL::undef_functions,
           which means all classes will inherit
           AAppaacchhee::::SSyymmbbooll::::uunnddeeff__ffuunnccttiioonnss.

       Others
           Module such as HHTTMMLL::::EEmmbbppeerrll and AAppaacchhee::::eePPeerrll who
           compile and script cache scripts ala Apache::Registry
           style can use undef_functions with this bit of code:
               if($package->can('undef_functions')) {
                   $package->undef_functions;
               }

           Where $package is the name of the package in which the
           script is being re-compiled.

SSEEEE AALLSSOO
       perlsub(1), Devel::Symdump(3)

AAUUTTHHOORR
       Doug MacEachern