Does capturing cost more in a regular expression matching?

According to perlre:

WARNING: Once Perl sees that you need one of $&, $‘, or $’ anywhere in the program, it has to provide them for every pattern match. This may substantially slow your program. Perl uses the same mechanism to produce $1, $2, etc, so you also pay a price for each pattern that contains capturing parentheses. (To avoid this cost while retaining the grouping behaviour, use the extended regular expression "(?: ... )" instead.) But if you never use $&, $‘ or $’, then patterns without capturing parentheses will not be penalized. So avoid $&, $’, and $‘ if you can, but if you can’t (and some algorithms really appreciate them), once you’ve used them once, use them at will, because you’ve already paid the price. As of 5.005, $& is not so costly as the other two.
So there will be some minor overhead in using capturing parentheses.

In reply to Re^3: Back reference in s///g ? by jwkrahn
in thread Back reference in s///g ? by Anonymous Monk

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