>>> [] !!? 0 Nothing
>>> ["a", "b", "c"] !!? 3 Nothing
>>> [1, 2, 3] !!? (-1) Nothing
>>> ["a", "b", "c"] !!? 2 Just "c"
>>> maybeAt 0 [] Nothing
>>> maybeAt 3 ["a", "b", "c"] Nothing
>>> maybeAt (-1) [1, 2, 3] Nothing
>>> maybeAt 2 ["a", "b", "c"] Just "c"