What you probably want to do is a recursive print of the objects. Something like (total pseudo-code)-

sub dump_tree {
    my $thing = shift;
    print "<div>";
    dump_tree($_) for $thing->kids;
    print $thing if $thing->is_printable;
    print "</div>";
}
[download]

And then your CSS basically takes care of itself. And you can do things like this-

/* Take these as deep as you need/want and apply.class */
div { background-color: #111; }
div>div { background-color: #611; }
div>div>div{ background-color: #161; }
div>div>div>div { background-color: #116; }
[download]

Sadly, you can't recurse += with the CSS but you could certainly write the CSS with Perl to go as deep as you like/need and manipulate the layout variables programmatically/progressively.

.