Probably not the "best", but I have one that make somewhat clever use of its placement in a subroutine to work in one line without creating a lexical. I'll put here the whole test program.

#!/usr/bin/perl -w
use strict;

my $foo = shift;

sub one {
    return shift;
}

sub two {
    push @_, one( $foo ) and $_[0] ? return pop : pop;
    return "No arg";
}

print two() . "\n";;
[download]

Maybe useful if you're looking for some obfuscation. It works with unshift/shift as well, of course.