(define a (list 1 2 3 4))
(define b (list a 'x 'y 'z))
(define c (list b 'x1 'y1 'z1))
(gc)
(check (and
(eq a (list 1 2 3 4))
(eq b (list (list 1 2 3 4) 'x 'y 'z))
(eq c (list (list (list 1 2 3 4) 'x 'y 'z) 'x1 'y1 'z1))))