Actually I meant (?>(?>[^{}]*)|\{(??{$parens})\})*, since I don't see a reason why any of these groups should ever give up something that they successfully matched.

For an explanation of (?>...) see How backtracking works in regular expressions and Avoiding regex backtracking.

In reply to Re^3: balanced parens regexp hangs by moritz
in thread balanced parens regexp hangs - solved by grizzley

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