I have a similar script that uses LWP::Simple, Digest::MD5 and DBI. I basically store the page checksum in the DB, which is a pretty good method to check if the file has changed. Comparing the full page is kinda overkill IMHO.
Update: pretty similar to mr.nick's solution above...
Update2: I was actually considering posting this under CUFP a few days ago...

#!/usr/bin/perl -w

use strict;
use DBI;
use LWP::Simple;
use Digest::MD5  qw(md5 md5_hex md5_base64);

my $dbh = DBI->connect("dbi:mysql:database", "user", "password") || di
+e "Can't connect";

my $sth = $dbh->prepare("select url from sites");
$sth->execute();
my $url = undef;
$sth->bind_col(1,\$url);
my @urls = ();
while($sth->fetch()) { push(@urls, $url); }
$sth->finish();
if (@ARGV) 
{ my $url = $ARGV[0];
  my $page = get($url);
  my ($title) = $page =~ /<TITLE>(.*?)<\/TITLE>/i;
  my $digest = md5_hex($page);
  my $date = time();
  $title =~ s/\'/\\\'/g; 
  my $q = join ("','",$title,$url,$digest,$date);
  $q = "'".$q."'";
  $sth = $dbh->prepare("insert into sites values ('$title','$url','$di
+gest','$date')");
  $sth->execute();
}
$sth->finish();
foreach my $url (@urls) 
{ my $page = get($url);
  print $url,"\n";
  my $digest = md5_hex($page);
  $sth = $dbh->prepare("select checksum from sites where url = '$url'"
+);
  $sth->execute();
  my $checksum = undef;
  $sth->bind_col(1,\$checksum);
  while($sth->fetch)
  { if ($checksum ne $digest)
    { my $date = time();
      my ($title) = $page =~ /<TITLE>(.*?)<\/TITLE>/i;
      my $q = qq|url = "$url", name = "$title", checksum = "$digest", 
+date = "$date"|;
      my $sth2 = $dbh->prepare("update sites set $q where url = '$url'
+");
      $sth2->execute(); 
    }
  }
  $sth->finish();
} 

$dbh->disconnect || die "Disconnection failed";
[download]

Greetz
Beatnik
... Quidquid perl dictum sit, altum viditur.