{
    my $counter = 'x0000';
    sub give_id {
      my $x = $_[0];
      $x->attr('id', $counter++) unless defined $x->attr('id');
      foreach my $c ($x->content_list) {
        give_id($c) if ref $c; # ignore text nodes
      }
    };
    give_id($start_node);
  }
##</code><code>##

my $tree = HTML::TreeBuilder->new_from_content($html);
$tree->elementify();
my $tagmap = $tree->tagname_map();
ok('Matrix' eq $$tagmap{'h2'}[1]{'_content'}[0], "Got correct title (Matrix)");

##</code><code>##

func textfromxml($xp, $xpath) {
    my $nodeset = $xp->find($xpath);
    my ($text) = XML::XPath::XMLParser::as_string(($nodeset->get_nodelist)[0])
        =~ />(.*)</;
    return $text;
}

use XML::XPath;
use XML::XPath::XMLParser;
my $xp = XML::XPath->new(xml => $html);
my $text = textfromxml($xp, '/html/body/div/div/h2[2]');
ok('Matrix' eq $text, "Got correct title (Matrix)");