Description:
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The (?{CODE}) regular expression has been in Perl since <= 5.005, and 
the PHP documentation for PCRE says that it's current as of 5.005. This 
functionality does not appear to be functional in PHP 5.2.9.

Reproduce code:
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<?

$pattern = '/^(?{ $d=0 })(?:\((?{$d++})|\)(?{$d--})(?(?{$d<0})(?!))|(?>[^()]*))*(?(?{$d!=0})(?!))$/';

$pattern_simple = '/^(?{$d=0})\(/';

$subject = '((I)(like(pie))!)';

echo "result: ".preg_match($pattern, $subject)."<br/>";

echo "result_simple: ".preg_match($pattern_simple, $subject)."<br/>";

?>

Expected result:
----------------
I'm not claiming that the regular expressions should produce a match, 
but they should compile and be evaluated, and thus return either a 0 or 
a 1.

Actual result:
--------------
Warning: preg_match() [function.preg-match]: Compilation failed: 
unrecognized character after (? or (?- at offset 2 in __FILE__ on line 
__LINE__