(shuffle '(a b) '(c d))
;Value 13: ((a b c d) (a c b d) (a c d b) (c a b d) (c a d b) (c d a b))
(shuffle '(a b c) '(1 2 3))
;Value 14: ((a b c 1 2 3) (a b 1 c 2 3) (a b 1 2 c 3) (a b 1 2 3 c)
(a 1 b c 2 3) (a 1 b 2 c 3) (a 1 b 2 3 c) (a 1 2 b c 3) (a 1 2 b 3 c)
(a 1 2 3 b c) (1 a b c 2 3) (1 a b 2 c 3) (1 a b 2 3 c) (1 a 2 b c 3) (1 a 2 b 3 c)
(1 a 2 3 b c) (1 2 a b c 3) (1 2 a b 3 c) (1 2 a 3 b c) (1 2 3 a b c))
You can see that the letters a, b, c are never scrambled relative to each
other; the same is true of the numbers 1, 2 and 3. The letters and the
numbers are shuffled, they are not scrambled (permuted).