Did you read the POD for this method?
look_down
@elements = $h->look_down( ...criteria... );
$first_match = $h->look_down( ...criteria... );
This starts at $h and looks thru its element descendants (in pre-order), looking for elements matching the criteria you specify. In list context, returns all elements that match all the given criteria; in scalar context, returns the first such element (or undef, if nothing matched).
my $table = $h->look_down('_tag', 'table');
my @rows = $table->look_down(_tag => 'td', class => qr/HeaderTitle\b?/
+);