Also, be aware that Perl supports arbitrary size integers via the core Math::BigInt module. For example:

use Math::BigInt;
my $x = Math::BigInt->new('123456789012345678901234567890');
my $y = '123456789012345678901234567890';
$x += 1;
$y += 1;
print "x=$x\n";
print "y=$y\n";
[download]

prints:

x=123456789012345678901234567891
y=1.23456789012346e+029
[download]

Update: See also bigint and bignum.