Sub::Uplevel(3pm)

1Sub::Uplevel(3)       User Contributed Perl Documentation      Sub::Uplevel(3)
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NAME

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

9       This documentation describes version 0.18
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SYNOPSIS

12         use Sub::Uplevel;
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14         sub foo {
15             print join " - ", caller;
16         }
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18         sub bar {
19             uplevel 1, \&foo;
20         }
21
22         #line 11
23         bar();    # main - foo.plx - 11
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DESCRIPTION

26       Like Tcl's uplevel() function, but not quite so dangerous.  The idea is
27       just to fool caller().  All the really naughty bits of Tcl's uplevel()
28       are avoided.
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30       THIS IS NOT THE SORT OF THING YOU WANT TO DO EVERYDAY
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32       uplevel
33             uplevel $num_frames, \&func, @args;
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35           Makes the given function think it's being executed $num_frames
36           higher than the current stack level.  So when they use call‐
37           er($frames) it will actually give caller($frames + $num_frames) for
38           them.
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40           "uplevel(1, \&some_func, @_)" is effectively "goto &some_func" but
41           you don't immediately exit the current subroutine.  So while you
42           can't do this:
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44               sub wrapper {
45                   print "Before\n";
46                   goto &some_func;
47                   print "After\n";
48               }
49
50           you can do this:
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52               sub wrapper {
53                   print "Before\n";
54                   my @out = uplevel 1, &some_func;
55                   print "After\n";
56                   return @out;
57               }
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EXAMPLE

60       The main reason I wrote this module is so I could write wrappers around
61       functions and they wouldn't be aware they've been wrapped.
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63           use Sub::Uplevel;
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65           my $original_foo = \&foo;
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67           *foo = sub {
68               my @output = uplevel 1, $original_foo;
69               print "foo() returned:  @output";
70               return @output;
71           };
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73       If this code frightens you you should not use this module.
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BUGS and CAVEATS

76       Well, the bad news is uplevel() is about 5 times slower than a normal
77       function call.  XS implementation anyone?
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79       Sub::Uplevel overrides CORE::GLOBAL::caller temporarily for the scope
80       of each uplevel call.  It does its best to work with any previously
81       existing CORE::GLOBAL::caller (both when Sub::Uplevel is first loaded
82       and within each uplevel call) such as from Contextual::Return or
83       Hook::LexWrap.
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85       However, if you are routinely using multiple modules that override
86       CORE::GLOBAL::caller, you are probably asking for trouble.
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HISTORY

89       Those who do not learn from HISTORY are doomed to repeat it.
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91       The lesson here is simple:  Don't sit next to a Tcl programmer at the
92       dinner table.
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THANKS

95       Thanks to Brent Welch, Damian Conway and Robin Houston.
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AUTHORS

98       David A Golden <dagolden@cpan.org> (current maintainer)
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100       Michael G Schwern <schwern@pobox.com> (original author)
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LICENSE

103       Original code Copyright (c) 2001 to 2007 by Michael G Schwern.  Addi‐
104       tional code Copyright (c) 2006 to 2007 by David A Golden.
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106       This program is free software; you can redistribute it and/or modify it
107       under the same terms as Perl itself.
108
109       See http://www.perl.com/perl/misc/Artistic.html
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