I would politely disagree with your interpretation, as the two approaches are functionally equivalent. There was no mention of side effects/counting in the OP, and so judging the proposed solution on those grounds is inappropriate. It is an inferior algorithm and likely a bad habit, but the code does the job and does it in a straight-forward fashion. If I'd spent more brain power considering the question, I would have substituted + for *. The modification actually occurred to me after I posted but before I'd read your comments. However, I try to avoid correcting posts for stylistic reasons alone to avoid versioning confusion and race conditions.

I agree that the \K construct is the most elegant and appropriate solution, but not everyone runs 5.10 - my external server runs 5.8. The alternate choice option I list seems the most transparent for a neophyte to my eye, but I expect to be the the most expensive given the e modifier.