push (\u1 -> (\u2 -> u1 Term))
<hidden>:
| catchFail
|   <try>
|   | push (\u1 -> (\u2 -> (\u3 -> 'r' : u2 u3)))
|   | read ('r' ==)
|   | lift (\u1 -> (\u2 -> u1 u2))
|   | call <hidden>
|   | lift (\u1 -> (\u2 -> u1 u2))
|   | popFail
|   | ret
|   <handler>
|     pushInput
|     lift Term
|     choices [(\u1 -> u1)]
|       <branch>
|       | push (\u1 -> u1)
|       | ret
|       <default>
|         fail
call <hidden>
lift (\u1 -> (\u2 -> u1 u2))
<hidden>:
| lift (\u1 -> (\u2 -> u1 u2))
| ret
catchFail
  <try>
  | catchFail
  |   <try>
  |   | pushInput
  |   | read (\u1 -> Term)
  |   | pop
  |   | popFail
  |   | loadInput
  |   | fail
  |   <handler>
  |     loadInput
  |     push Term
  |     popFail
  |     refJoin <hidden>
  <handler>
    pushInput
    lift Term
    choices [(\u1 -> u1)]
      <branch>
      | fail
      <default>
        fail