The other one I want occassionally is "or".

Imagine Left and Right contained data of compatible types, then I'd like to extract that data (regardless of tag) like so:

    if x is Left(y) or x is Right(y) then ...

That way I only need to write the `...` part once. (This could be combined with the rest of the pattern matching machinery in interesting ways, and would probably need to have eager matching / short-circuiting semantics in case both cases match).