NAME

       Return::MultiLevel - return across multiple call levels

SYNOPSIS

         use Return::MultiLevel qw(with_return);

         sub inner {
           my ($f) = @_;
           $f->(42);  # implicitly return from 'with_return' below
           print "You don't see this\n";
         }

         sub outer {
           my ($f) = @_;
           inner($f);
           print "You don't see this either\n";
         }

         my $result = with_return {
           my ($return) = @_;
           outer($return);
           die "Not reached";
         };
         print $result, "\n";  # 42

DESCRIPTION

       This module provides a way to return immediately from a deeply nested call stack. This is
       similar to exceptions, but exceptions don't stop automatically at a target frame (and they
       can be caught by intermediate stack frames using "eval"). In other words, this is more
       like setjmp(3)/longjmp(3) than "die".

       Another way to think about it is that the "multi-level return" coderef represents a
       single-use/upward-only continuation.

   Functions
       The following functions are available (and can be imported on demand).

       with_return BLOCK
           Executes BLOCK, passing it a code reference (called $return in this description) as a
           single argument. Returns whatever BLOCK returns.

           If $return is called, it causes an immediate return from "with_return". Any arguments
           passed to $return become "with_return"'s return value (if "with_return" is in scalar
           context, it will return the last argument passed to $return).

           It is an error to invoke $return after its surrounding BLOCK has finished executing.
           In particular, it is an error to call $return twice.

DEBUGGING

       This module uses "unwind" from "Scope::Upper" to do its work. If "Scope::Upper" is not
       available, it substitutes its own pure Perl implementation. You can force the pure Perl
       version to be used regardless by setting the environment variable "RETURN_MULTILEVEL_PP"
       to 1.

       If you get the error message "Attempt to re-enter dead call frame", that means something
       has called a $return from outside of its "with_return { ... }" block. You can get a stack
       trace of where that "with_return" was by setting the environment variable
       "RETURN_MULTILEVEL_DEBUG" to 1.

BUGS AND LIMITATIONS

       You can't use this module to return across implicit function calls, such as signal
       handlers (like $SIG{ALRM}) or destructors ("sub DESTROY { ... }").  These are invoked
       automatically by perl and not part of the normal call chain.

SUPPORT AND DOCUMENTATION

       After installing, you can find documentation for this module with the "perldoc" command.

           perldoc Return::MultiLevel

       You can also look for information at <https://metacpan.org/pod/Return::MultiLevel>.

       To see a list of open bugs, visit
       <https://rt.cpan.org/Public/Dist/Display.html?Name=Return-MultiLevel>.

       To report a new bug, send an email to "bug-Return-MultiLevel [at] rt.cpan.org".

AUTHOR

       Lukas Mai, "<l.mai at web.de>"

COPYRIGHT & LICENSE

       Copyright 2013-2014 Lukas Mai.

       This program is free software; you can redistribute it and/or modify it under the terms of
       either: the GNU General Public License as published by the Free Software Foundation; or
       the Artistic License.

       See <http://dev.perl.org/licenses/> for more information.