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Re^2: regex anchoring issue

by smls (Friar)
on Feb 15, 2013 at 11:23 UTC ( #1018879=note: print w/replies, xml ) Need Help??


in reply to Re: regex anchoring issue
in thread regex anchoring issue

Why do you place the regex in a (?>...) non-backtracking group?

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Re^3: regex anchoring issue
by kcott (Chancellor) on Feb 16, 2013 at 05:58 UTC

    Wrapping regexp alternations in (?>...) is something I do by default. While there may be rare cases where this might be problematical, I haven't encountered any: it's something that doesn't hurt and, indeed, often helps.

    This usage is based on a "Perl Best Practices" guideline: Backtracking (page 269). It's summarised on page 271 as:

    ... rewrite any instance of:

    X | Y

    as:

    (?> X | Y )

    While I'm not a slave to all "Perl Best Practices" guidelines, this is one I have found to be useful.

    Update: s/have encountered/haven't encountered/

    -- Ken

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[Lady_Aleena]: atcroft. maybe look at raw PODs. There is also L<foo|http://foo. com> and some might be linking directly to meta::cpan.
[Lady_Aleena]: Oops, didn't read the L<text|url> right.
[atcroft]: Lady_Aleena: I considered it a violation of the principle of least surprise, but before I tried sending a message to the particular author (and perhaps make myself appear more foolish than normal), I wanted to find out if there was a more site-agnostic
[atcroft]: way (since I am guessing that MetaCPAN may be the author's preferred CPAN interface).

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