How can I swap two Perl variables without using the third?

Question

I want to swap two variables values without using the third variable in Perl, e. g.:

my $first = 10;
my $second = 20;

Please suggest me how

Answer 1

The Perl-specific methods already listed are best, but here's a technique using XOR that works in many languages, including Perl:

use strict;

my $x = 4;
my $y = 8;

print "X: $x  Y: $y\n";

$x ^= $y;
$y ^= $x;
$x ^= $y;

print "X: $x  Y: $y\n";

X: 4  Y: 8
X: 8  Y: 4