.
         .
         .
  ($rold ^ $rnew) =~ /^\0*/ and my $lsubscr = (-$+[0] + 1 && $+[0]) ? -$+[0] + 1 : length $new;
   my $losubscr = ($lsubscr == length $new) ? length $old : $lsubscr;
   substr $old, $losubscr, 0, '</span>';
         .
         .
         .