use storable;

my $results = retrieve('results_store');

sub check_site {
  my $domain = shift;
  my $current_result = check_domain($domain);
  my $last_result = $results->{$domain};
  if (($last_result == 200 || !$last_result) && $current_result == 400) {
    send_email($domain);
  }

  if ($last_result != $current_result) { 
    $results->{$domain} = $current_result;
    store $results, 'results_store'; 
  }
}