Can you salvage my negative lookbehind example for commifying numbers?

Question

In the \"Advanced Regular Expresssion\" chapter in Mastering Perl, I have a broken example for which I can\'t figure out a nice fix. The example is perhaps trying to be too clev

Answer 1

I don't think this is what you are after (especially becaue the negative look-behind assertion has been dropped), but I guess, your only option is to slurp up the decimal places like in this example:

s/
  (?:
    (?<=\d)
    (?=(?:\d\d\d)+\b)
   |
    ( \d{0,3} \. \d+ )
  )
 / $1 ? $1 : ',' /exg;

P.S. I think it is a good example when not used as the first one in the book, as it demonstrates some of the pitfalls and limitations of look-around assertions.