I can't explain the second issue, but the first is your bug. Returning undef explicitly to indicate falsehood is almost always an error. There are two circumstances where it's okay:

I don't think the second case is that useful; bare return does the right thing for you.

In reply to Re: Potential Tie::Memoize Bug by chromatic
in thread Potential Tie::Memoize Bug by satchm0h

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