Make2.SyntaxMonadic operators, see Monad.Syntax.S2 for more.
f >=> g is fun x -> f x >>= g
val (!!) : 'a -> ('a, 'e) T2(M).t!!x is return x
!$$f is Lift.binary f
val (!$$$) : 
  ('a -> 'b -> 'c -> 'd) ->
  ('a, 'e) T2(M).t ->
  ('b, 'e) T2(M).t ->
  ('c, 'e) T2(M).t ->
  ('d, 'e) T2(M).t!$$$f is Lift.ternary f