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<?php pattern="\( ( (?>[^()]+) | (?R) )* \)"; str="(def a (x) (+ 1 x))(print (a 1))"; var_dump(preg_grep(pattern,str));
Output for 5.3.0 - 5.3.28, 5.4.0 - 5.4.26
Parse error: syntax error, unexpected '=' in /in/7inCS on line 3
Process exited with code 255.
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178.29 ms | 1395 KiB | 63 Q