Reversing the string requires reversing the regex pattern too, and that's not trivial. For example, (?<=(.).*\1) would try to match \1.*(.), but \1 hasn't been populated yet.

Update:

... What am I saying! Just have people write (.).*\1. That's what they'd have to do with a right-to-left parser too. I suspect all issues can be solved with proper documentation.

In reply to Re^4: Why is variable length lookahead implemented while lookbehind is not? by ikegami
in thread Why is variable length lookahead implemented while lookbehind is not? by Kc12349

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