(command.CommandList
  children: [
    (C {(echo)} {(SQ <'--- pgrphack insists on an argument'>)})
    (command.CommandList
      children: [
        (command.Sentence child:(C {(pgrphack)}) terminator:<Op_Semi ';'>)
        (C {(echo)} {($ VSub_QMark '$?')})
      ]
    )
    (C {(echo)} {(SQ <'--- pgrphack complains if it cannot run program'>)})
    (command.CommandList
      children: [
        (command.Sentence child:(C {(pgrphack)} {(./nonexistent)}) terminator:<Op_Semi ';'>)
        (C {(echo)} {($ VSub_QMark '$?')})
      ]
    )
    (C {(echo)} {(SQ <'--- pgrphack runs a program'>)})
    (command.CommandList
      children: [
        (command.Sentence child:(C {(pgrphack)} {(echo)} {(ok)}) terminator:<Op_Semi ';'>)
        (C {(echo)} {($ VSub_QMark '$?')})
      ]
    )
  ]
)