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

If you have to post on Stack Overflow asking if somebody can figure out how to do this with negative lookbehind, then it's obviously not a good example of negative lookbehind. You'd be better off thinking up a new example rather than trying to salvage this one.

In that spirit, how about an automatic spelling corrector?

s/(?

(Obviously, that's not a hard and fast rule in English, but I think it's a more realistic application of negative lookbehind.)