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

use WWW::Mechanize;
use HTML::Scrubber;
use HTML::Entities;
use Regexp::Common qw(net);

our $USER = 'admin';
our $PASS = 'secret';

my $mech = new WWW::Mechanize autocheck => 1;
my $scrubber = new HTML::Scrubber;

my $gateway_ip = '192.168.1.1:80';
$mech->credentials( 
  $gateway_ip, 'Linksys BEFSR41/BEFSR11/BEFSRU31', $USER, $PASS);
$mech->get("http://$gateway_ip/Status.htm");
my $content = $mech->content;
my ($html) = ($content =~ /WAN head-->(.*?)<!--WAN tail/);
$html = decode_entities($scrubber->scrub($html));
my ($ip) = ($html =~ /IP Address:($RE{net}{IPv4})/);
$ip or die "IP not found.";

print "$ip\n";