(Program
  (If
  { (Identifier)
  ->(Identifier) }
    (
    {-(Identifier)-}
      (Identifier)
    {+(Identifier)+})
  { (Empty)
  ->(If
    {+(Identifier)+}
    {+(
      {+(Identifier)+}
      {+(Identifier)+})+}
    {+(
      {+(Identifier)+}
      {+(Identifier)+})+}) }))