in reply to RegEx Problem

Here's one I hadn't tried before -- /e nested within /e. 
$phrase = "NoMatch cowsCanFly sheepAreVeryCool NoMatch";

$phrase =~ s{
               \b
               (
                  [a-z]+
                  (?:[A-Z][a-z]+)+
               )
               \b
            }{
               my $word = $1;
               $word =~ s/([A-Z])/"-" . lc($1)/eg;
               $word;
            }gex;

print $phrase, "\n";

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Re: Re: RegEx Problem
by samtregar (Abbot) on May 29, 2002 at 06:26 UTC
    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

[reply]
      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

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

        -sam

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