k, newbie answer ahead. Something like this gave me the proper answer 0||1 for equality using String::Approx. Of course not any validity against proper html code or anything, just plain text match.

use String::Approx 'amatch';
$match = amatch(@txt1, @txt2));
[download]

where @txt1 is the original document and @txt2 is the comparing document. And $match will give you 0||1 for the match.