print cmpHtml(
    '<p><font foo="bar" bar="1">bar 1</font></p>',
    '<p><font bar="2" foo="bar">bar 1</font></p>'
);

##</code><code>##

print cmpHtmlElt ($elt1, $elt2);

##</code><code>##

sub cmpHtml {
    my ($html1, $html2) = @_;
    my $root1 = HTML::TreeBuilder->new;
    my $root2 = HTML::TreeBuilder->new;

    $root1->parse_content ($html1);
    $root1->elementify    ();
    $root2->parse_content ($html2);
    $root2->elementify    ();

    return cmpHtmlElt ($root1, $root2);
}

sub cmpHtmlElt {
    my ($elt1, $elt2) = @_;

    my $cmp = defined $elt1 cmp defined $elt2;
    return $cmp if $cmp;
    return 0 unless defined $elt1;

    $cmp = ref $elt1 cmp ref $elt2;
    return $cmp if $cmp;
    return $elt1 cmp $elt2 unless ref $elt1;

    $cmp = $elt1->tag () cmp $elt2->tag ();
    return $cmp if $cmp;

    my %attribs1 = $elt1->all_attr ();
    my %attribs2 = $elt2->all_attr ();

    $cmp = keys %attribs1 <=> keys %attribs2;
    return $cmp if $cmp;

    for my $key (keys %attribs1) {
        return 1 unless exists $attribs2{$key};
        next if $key =~ /^_/;

        $cmp = $attribs1{$key} cmp $attribs2{$key};
        return $cmp if $cmp;
    }

    my @children1 = $elt1->content_list ();
    my @children2 = $elt2->content_list ();

    $cmp = @children1 <=> @children2;
    return $cmp if $cmp;

    for my $index (0 .. $#children1) {
        $cmp = cmpHtmlElt ($children1[$index], $children2[$index]);
        return $cmp if $cmp;
    }
}