Thank you, that makes sense. I did indeed think backtracking could not occur within (?>PAT). This may be the first time I've tried to use (?>PAT) and I can't say that reading the documentation really helped understand where backtracking was being suppressed.

The quantifier+ (possessive quantifier) syntax is new to me. Any idea when it was introduced (5.10 maybe)? The phrase "give nothing back" in the documentation makes the possessive quantifier (and by implication (?>PAT) ) much easier to understand in my view.