(Program
  (Call
    (Identifier)
  {-(Identifier)-}
    (Identifier)
  {+(Identifier)+}
    (Empty))
  (Call
    (Identifier)
  { (Identifier)
  ->(Identifier) }
    (Empty))
  (Call
    (Identifier)
    (Or
      (Integer)
      (Integer))
    (Empty))
  (Call
    (Identifier)
  {-(Or
    {-(Integer)-}
    {-(Integer)-})-}
    (Or
      (Integer)
      (Integer))
  {+(Or
    {+(Integer)+}
    {+(Integer)+})+}
    (Empty)))