After reading your replies to further questions, it sounds like you don't really need something that truely understands html to the fullest, but a parser that groks the concept of text, html tags and their attributes, and html comments.

My suggestion would be to write something that can pick apart those 3 things and do the small edits you need them to and reassemble the file, mal-formedness and all.

If you proceed down the path that the browsers did and try to guess a documents meaning (via your own code or a module), I believe you'll end up far too often fixing html by hand, either on the way in or the way out and much sadness will ensue.

To offer at least something and not leave you with, "Oh ya that sucks. Good luck!" Here's a bit code that might help. It's inefficient, but ok for moderate sized data. (I just happened to run across this yesterday in my playground/lets-see-if-I-can-do-X perl script dir):

sub parse {
   my $source = shift ;
   my @output ;
   while ( $source =~ s/^([<]*)<//s ) {
      push @output, [ 'text', $1 ] if $1 ne '' ;
      $source =~ s/^([^\s>]*)([\s>])//s ;
      my $tag = $1 ;
      if ( $tag eq '!--' ) {
         $source =~ s/^(.*?)-->//s ;
         push @output, [ 'comment', $1 ] ;
      } else {
         my $param = '' ;
         if ( $2 ne '>' ) {
            while ( $source =~ s/^([^'">]*)(["'>])//s ) {
               $param .= $1 ;
               last if $2 eq '>' ;
               my $quote = $2 ;
               $source =~ s/^([^$quote]*$quote)// ;
               $param .= $quote . $1 . $quote ;
            }
         }
         push @output, ['tag', $tag, $param ] ;
      }
   }
   return @output ;
}
[download]

What it does is takes a whole file and returns you an array of array refs. Each array ref contains 2 or 3 elements: what type of data it was (text, tag, comment), the data itself (minus the actual markup in the case of tags), and if the type is a tag, then the 3rd element is tag params.

HTH

-Ducky