Many thanks! I didn't know about warnings. But I noticed new issue. The problem is that when this warning appears the regex doesn't match...
It's not a new issue it's the same issue :) The recursion depth is limited to prevent catastrophic backtracking (mkay I think it's not actually recursion but it's called that in the docs). Doesn't Friedl describe that in his book? Add use diagnostics; to your program.

In reply to Re^3: Strange behaviour of the regex engine (pathological protection) by Anonymous Monk
in thread Strange behaviour of the regex engine by thof

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