require HTML::TokeParser;

while $file (@files) {
   my $p = HTML::TokeParser->new(file);
   my $match = 0;
   while(my $token = $p->get_token) {
       next unless @$token[0] eq 'T';
       if(index @$token[1], $SUBSTR) {
           $match = 1;
           last;
       }
   }
   if($match) {
       print $file, "\n";
   }
}