Same as Infix, except the monad type has two arguments. The second is always just passed through.
type ('a, 'e) t
val (>>=) : ('a, 'e) t ‑> ('a ‑> ('b, 'e) t) ‑> ('b, 'e) t
val (>>|) : ('a, 'e) t ‑> ('a ‑> 'b) ‑> ('b, 'e) t