in reply to Re: RegEx Problem
in thread RegEx Problem

If that works it's only because you got lucky. In general the regex engine is not reentrant. Seg-faults are the most common result of this kind of code...

-sam

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Re: Re: Re: RegEx Problem
by broquaint (Abbot) on May 29, 2002 at 10:30 UTC
    Nope, the regex is fine as it isn't re-entrant. If there was regex *within* the regex then that would be re-entrant, but as far as perl is concerned you can do as you please in the replace part of a s///.

    So this code will break[1] 

    my $str = "foo bar baz quux";
   $str =~ s<([a-z]+)
             (?{ s| \1|\L$&|; })><\U$1>xg;

    [download]
    But this is fine 
    $str =~ s<([a-z]+ ?)><local $_ = $1; s/$1/\U$&/g; $_>eg;

    [download]

    HTH

    _________
    broquaint

    [1] in theory, I'll be happy to change it to a proper re-entrant regex if someone will provide me with one

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[d/l]
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      D'oh. I stand corrected. Is this documented anywhere that you know of?

      -sam

[reply]
        I can't find anywhere in the distribution docs or any books I've searched so far that mention the problem of re-entrancy in regexes. I'm fairly sure it's covered in the monastery somewhere and has definitely been covered a few times in p5p.
        HTH

        _________
        broquaint

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