NAME
   Sub::Uplevel - apparently run a function in a higher stack frame

VERSION
   version 0.25

SYNOPSIS
     use Sub::Uplevel;

     sub foo {
         print join " - ", caller;
     }

     sub bar {
         uplevel 1, \&foo;
     }

     #line 11
     bar();    # main - foo.plx - 11

DESCRIPTION
   Like Tcl's uplevel() function, but not quite so dangerous. The idea is
   just to fool caller(). All the really naughty bits of Tcl's uplevel()
   are avoided.

   THIS IS NOT THE SORT OF THING YOU WANT TO DO EVERYDAY

   uplevel
         uplevel $num_frames, \&func, @args;

       Makes the given function think it's being executed $num_frames
       higher than the current stack level. So when they use
       caller($frames) it will actually give caller($frames + $num_frames)
       for them.

       "uplevel(1, \&some_func, @_)" is effectively "goto &some_func" but
       you don't immediately exit the current subroutine. So while you
       can't do this:

           sub wrapper {
               print "Before\n";
               goto &some_func;
               print "After\n";
           }

       you can do this:

           sub wrapper {
               print "Before\n";
               my @out = uplevel 1, &some_func;
               print "After\n";
               return @out;
           }

       "uplevel" has the ability to issue a warning if $num_frames is more
       than the current call stack depth, although this warning is disabled
       and compiled out by default as the check is relatively expensive.

       To enable the check for debugging or testing, you should set the
       global $Sub::Uplevel::CHECK_FRAMES to true before loading
       Sub::Uplevel for the first time as follows:

           #!/usr/bin/perl

           BEGIN {
               $Sub::Uplevel::CHECK_FRAMES = 1;
           }
           use Sub::Uplevel;

       Setting or changing the global after the module has been loaded will
       have no effect.

EXAMPLE
   The main reason I wrote this module is so I could write wrappers around
   functions and they wouldn't be aware they've been wrapped.

       use Sub::Uplevel;

       my $original_foo = \&foo;

       *foo = sub {
           my @output = uplevel 1, $original_foo;
           print "foo() returned:  @output";
           return @output;
       };

   If this code frightens you you should not use this module.

BUGS and CAVEATS
   Well, the bad news is uplevel() is about 5 times slower than a normal
   function call. XS implementation anyone? It also slows down every
   invocation of caller(), regardless of whether uplevel() is in effect.

   Sub::Uplevel overrides CORE::GLOBAL::caller temporarily for the scope of
   each uplevel call. It does its best to work with any previously existing
   CORE::GLOBAL::caller (both when Sub::Uplevel is first loaded and within
   each uplevel call) such as from Contextual::Return or Hook::LexWrap.

   However, if you are routinely using multiple modules that override
   CORE::GLOBAL::caller, you are probably asking for trouble.

   You should load Sub::Uplevel as early as possible within your program.
   As with all CORE::GLOBAL overloading, the overload will not affect
   modules that have already been compiled prior to the overload. One
   module that often is unavoidably loaded prior to Sub::Uplevel is
   Exporter. To forcibly recompile Exporter (and Exporter::Heavy) after
   loading Sub::Uplevel, use it with the ":aggressive" tag:

       use Sub::Uplevel qw/:aggressive/;

   The private function "Sub::Uplevel::_force_reload()" may be passed a
   list of additional modules to reload if ":aggressive" is not aggressive
   enough. Reloading modules may break things, so only use this as a last
   resort.

   As of version 0.20, Sub::Uplevel requires Perl 5.6 or greater.

HISTORY
   Those who do not learn from HISTORY are doomed to repeat it.

   The lesson here is simple: Don't sit next to a Tcl programmer at the
   dinner table.

THANKS
   Thanks to Brent Welch, Damian Conway and Robin Houston.

   See http://www.perl.com/perl/misc/Artistic.html

SEE ALSO
   PadWalker (for the similar idea with lexicals), Hook::LexWrap, Tcl's
   uplevel() at http://www.scriptics.com/man/tcl8.4/TclCmd/uplevel.htm

SUPPORT
 Bugs / Feature Requests
   Please report any bugs or feature requests through the issue tracker at
   <https://github.com/dagolden/Sub-Uplevel/issues>. You will be notified
   automatically of any progress on your issue.

 Source Code
   This is open source software. The code repository is available for
   public review and contribution under the terms of the license.

   <https://github.com/dagolden/Sub-Uplevel>

     git clone https://github.com/dagolden/Sub-Uplevel.git

AUTHORS
   *   Michael Schwern <[email protected]>

   *   David Golden <[email protected]>

CONTRIBUTORS
   *   Adam Kennedy <[email protected]>

   *   Alexandr Ciornii <[email protected]>

   *   Michael Gray <[email protected]>

COPYRIGHT AND LICENSE
   This software is copyright (c) 2015 by Michael Schwern and David Golden.

   This is free software; you can redistribute it and/or modify it under
   the same terms as the Perl 5 programming language system itself.

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