sub hash_to_html {
  my $x = shift;
  return "" unless ref($x) eq "HASH";
  return "<ul>".join("", map { "<li>$_\n".hash_to_html($x->{$_}) } sort keys %$x  )."</ul>\n";
}
$our_hash = {
	'Cows' => {
		'Brown' => undef,
		'Green' => undef,
		'Strawberry' => {
			'Spotted' => undef,
			'Solid' => undef
		},
		'Orange' => undef
	},
	'Dogs' => {
		'Purple' => {
			'Spotted' => undef,
			'Solid' => undef
		}
	}
};
print hash_to_html($our_hash);