207:0> a = [1,2,3,4]
[1, 2, 3, 4]
208:0> a[4] = a
[1, 2, 3, 4, [...]]
209:0> a[4]
[1, 2, 3, 4, [...]]
210:0> a[4][4]
[1, 2, 3, 4, [...]]
211:0> a[4][4][4][4][4][3]
4

have you ever used this technique? can you provide some example code
for us which illustrates any kind of usefulness of this that you can
imagine?