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Actually, I don't think we can remove A-Z from the pattern because that could be seen as a backward compatibility break. E.g. what if there's code out there that sets flags=0? Then the regexp wouldn't be case-insensitive and the removal of A-Z would break that code.

I think it is safe to swap a for -i though, so I'll do that. I'll also update the comment and, as I just also noticed, the documentation.