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

$first = $first + $second;
$second = $first - $second;
$first = $first-$second;

This will swap two integer variables A better solution might be

$first = $first xor $second;
$second = $first xor $second;
$first = $first xor $second;