#!/usr/bin/perl -w
use strict;

my $octet = q[0?\d\d?|1\d\d?|2[0-4]\d?|25[0-5]|2[6-9]]; # MUST BE CONSTRAINED
my $ip = q[(?<!\d\.)] . join(q[\.], ( "($octet)" ) x 4) . q[(?!\.\d)];
my $rx = qr/$ip/;