catchException "fail"
  <try>
  | catchException "fail"
  |   <try>
  |   | pushValue (\u1 -> (\u2 -> 'a' : ('a' : Term)))
  |   | read ('a' ==)
  |   | lift2Value (\u1 -> (\u2 -> u1 u2))
  |   | read ('a' ==)
  |   | lift2Value (\u1 -> (\u2 -> u1 u2))
  |   | popException "fail"
  |   | popException "fail"
  |   | ret
  |   <handler>
  |     loadInput
  |     raiseException "fail"
  <handler>
    pushInput
    lift2Value Term
    choicesBranch [(\u1 -> u1)]
      <branch>
      | catchException "fail"
      |   <try>
      |   | pushValue (\u1 -> (\u2 -> 'a' : ('b' : Term)))
      |   | read ('a' ==)
      |   | lift2Value (\u1 -> (\u2 -> u1 u2))
      |   | read ('b' ==)
      |   | lift2Value (\u1 -> (\u2 -> u1 u2))
      |   | popException "fail"
      |   | ret
      |   <handler>
      |     loadInput
      |     raiseException "fail"
      <default>
        raiseException "fail"