#!/usr/bin/perl -w

use strict;
use LWP::UserAgent;

my $pageNew;

# I used the US version of http://www.theregister.co.uk/ as an example
my $siteName = 'http://www.theregus.com'; 

my $ua = LWP::UserAgent->new;

my $request = HTTP::Request->new('GET', "$siteName");
my $pageOld = $ua->request($request);

while() {
   
   sleep 1800; # 30 Minutes
   
   $pageNew = $ua->request($request);
   
   if ($pageOld->content ne $pageNew->content) {
      system('konqueror', $siteName)==0 
         or die "Unable to open browser\n";
         
      $pageOld = $pageNew;
   }         
}