#!/usr/bin/perl -w

use vars qw/$a $b/;
use strict;
use Benchmark;

$a = 0;
$b = 1;

sub traditional {
        my $c = $a;
        $a = $b;
        $b = $c;
}

sub arrays {
        ($b, $a) = ($a, $b);
}

sub xor {
        $a = $a ^ $b;
        $b = $a ^ $b;
        $a = $a ^ $b;
}

timethese(-5, {
        trad            => \&traditional,
        arrays  => \&arrays,
        xor             => \&xor,
        });

[ed@ci478467-a ed]$ perl swap.pl
Benchmark: running arrays, trad, xor, each for at least 5 CPU seconds...
    arrays:  5 wallclock secs ( 5.12 usr +  0.00 sys =  5.12 CPU) @ 24242.19/s (n=124120)
      trad:  6 wallclock secs ( 5.00 usr +  0.01 sys =  5.01 CPU) @ 40630.74/s (n=203560)
       xor:  5 wallclock secs ( 5.11 usr +  0.00 sys =  5.11 CPU) @ 30829.16/s (n=157537)