I don’t see how a string “null” would break anything besides a very stupidly written program (e.g., one which tries to eval() the input) or an ordinary program written in a very stupid language (e.g., one which tries to coerce strings to other types—PHP, is that you?).

I’m a big fan of pattern matching (especially statically verified pattern matching so sorry elixir), but I don’t see how it would help here.