m/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\$/;

##</code><code>##

use strict;
my @nums;
my $IP = "127.0.0.1"
(@nums) = $IP =~ m/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/;

# test each for <= 255 here.
# also make sure its not 0.0.0.0

##</code><code>##

m/^([01]?\d\d?|2[0-4]\d|25[0-5])\.([01]?\d\d?|2[0-4]\d|25[0-5])\.
   ([01]?\d\d?|2[0-4]\d|25[0-5])\.([01]?\d\d?|2[0-4]\d|25[0-5])$/;