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run code in 300+ PHP versions simultaneously
<?php $pattern="/\(((?>[^()]+)|(?R))*\)/"; //$str="(def a (x) (+ 1 x))(print (a 1))"; $str="(aaa)"; preg_match_all($pattern,$str,$out); var_dump($out);

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34.6 ms | 402 KiB | 5 Q