(Program
  (Call
    (Identifier)
  {+(Identifier)+}
    (Identifier)
    (Empty))
{+(Call
    (Identifier)
    (Identifier)
    (Empty))+}
{+(Context
    (Comment)
    (Empty))+}
{-(Context
    (Comment)
    (Call
      (Identifier)
      (Identifier)
      (Identifier)
      (Empty)))-})