I have to agree with tobyink on this one. Regexes are supposed to provide stable output given a set of well-defined rules (which thanks to p5p they pretty much always have, without fail). What's not well-defined is what steps the underlying implementation takes to arrive at the output, and that's a Good Thing, as some of the optimizations this enables are quite profound indeed. I don't get the sense that you (the OP) are advocating this weird execution side effect not working as being a bug that needs to be fixed, but nonetheless feel it important to underscore my own strong preference for end-result correctness first, performance second, and weird effects likely to break tomorrow coming in a distant third.

In reply to Re^2: Interesting behavior of regular expression engine by rjt
in thread Interesting behavior of regular expression engine by lightoverhead

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