$url = URI->new($url);

defined( my $host = $url->host() )
   or die("No host\n");

my $tld;
if ($host =~ /\./) {
   $tld = /\.([^.]+)$/;
   $tld =~ /[a-z]/i
      or die("No domain\n");
} else {
   $host =~ /[a-z]/i
      or die("No domain\n");
   $tld = 'localdomain';
}