sub delete_empty_list_item {
	my $xhtml = HTML::TreeBuilder->new;
	$xhtml->implicit_tags(1);
	$xhtml->parse_file($file);

	for my $list_item ($xhtml->findnodes('/html/body//div/ul/li')) {
		if ($list_item->is_empty) {
			print qq(DELETE\n);
			$list_item->delete();
		}
	}
    print $xhtml->as_XML_indented;
	$xhtml->eof;
}

OUTPUT:
<div>
	<ul>
		<li>one</li>
		<li>two</li>
		<li>three</li>
	</ul>
	<ul>
		<li>two</li>
	</ul>
	<ul>
	</ul>
</div>