: (let (X 1
      N (size Data))
   (loop
      (let E (get Data X)
         (cond
            ((== E 1)(put Data (get Data (+ X 3)) (+ (get Data (+ X 1)) (get Data (+ X 2)) ) ) )
            ((== E 2)(put Data (get Data (+ X 3)) (* (get Data (+ X 1)) (get Data (+ X 2)) ) ) )
            ((== E 99)(set X (+ N 1))) )
         (inc 'X 4) )
      (T (> X N) Data) ) )
!? (put Data (get Data (+ X 3)) (* (get Data (+ X 1)) (get Data (+ X 2))))
NIL -- Cons pair expected
?