If you don't put it there, the invocation of $re from within the first invocation of $re can just skip over text to find the parentheses within the quotes.

No, it can't skip. That's what I was showing. If it could skip, all the regexp in my parent post would match, since they would skip over the !. When using (??{ $re }), matching $re is anchored at the current pos..

In reply to Re^4: A regexp to parse nested brackets containing strings by ikegami
in thread A regexp to parse nested brackets containing strings by dfaure

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