REM Test passing a function to a function:
      PRINT FNtwo(FNone(), 10, 11)
      END

      REM Function to be passed:
      DEF FNone(x, y) = (x + y) ^ 2

      REM Function taking a function as an argument:
      DEF FNtwo(RETURN f%, x, y) = FN(^f%)(x, y)