Sub::Uplevel(3) User Contributed Perl Documentation Sub::Uplevel(3)NAMESub::Uplevel - apparently run a function in a higher stack frame
VERSION
This documentation describes version 0.2002
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 $num_frames
higher than the current stack level. So when they use call‐
er($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" will issue a warning if $num_frames is more than the cur‐
rent call stack depth.
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?
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.
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.
AUTHORS
David A Golden <dagolden@cpan.org> (current maintainer)
Michael G Schwern <schwern@pobox.com> (original author)
LICENSE
Original code Copyright (c) 2001 to 2007 by Michael G Schwern. Addi‐
tional code Copyright (c) 2006 to 2008 by David A Golden.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
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
perl v5.8.8 2008-09-12 Sub::Uplevel(3)
