While I agree in general, I'd not call it grind its performance to a halt.

If I remember correctly from previous explanations the impact of using one of those variables makes perl copy every string that you match a regex against.

How much that is strongly depend on your application, and might range from "not measurable" to "makes your application crash" (when it runs out of memory).

I find these variables very useful when debugging complicated regex. I put something like this into the regexes at various places: (?{ print "&`«$&»$'\n" }) which shows pretty nicely how far the regex engine proceeded so far. (But you won't find that in production code ;-)

In reply to Re^2: $& as a read-only value by moritz
in thread $& as a read-only value by frasco

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