lets
` <*>
  + pure Term
  ` <|>
    + try
    | ` <*>
    |   + <*>
    |   | + pure (\u1 -> (\u2 -> 'a' : ('a' : Term)))
    |   | ` satisfy
    |   ` satisfy
    ` try
      ` <*>
        + <*>
        | + pure (\u1 -> (\u2 -> 'a' : ('b' : Term)))
        | ` satisfy
        ` satisfy