Select Code to Download

$x =~ s{(?<=<td>)((?:(?!<td>).)*)3((?:(?!</td>).)*)(?=</td>)}{$1a$2};

$x =~ s{(?<=<td>)         # Start match with open-tag
        (                 # Capture
...
         </td>            #  then a close-tag
        )}                # End lookahead and pattern
       {$1a}x;