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Because once Perl sees that you need one of these variables anywhere in the
program, it has to provide them on each and every pattern match. The same
mechanism that handles these provides for the use of $1, $2, etc., so you
pay the same price for each regexp that contains capturing parentheses. But
if you never use $&, etc., in your script, then regexps without capturing parentheses won't 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.
Source: Perl FAQ: Regexps
Copyright: Copyright (c) 1997 Tom Christiansen and Nathan Torkington. |
Next: What good is \G in a regular expression?
Previous: Why don't word-boundary searches with \b work for me?
(Corrections, notes, and links courtesy of RocketAware.com)
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