dda,
I have been monitoring this thread for most of the day and as far as I can tell, no one has stated the obvious.

You would have (or could create) an infinite loop.

Cheers - L~R

Update: As fletcher_the_dog pointed this behavior does create the infinite loop for an array (not hash), and as pointed out by Mr. Muskrat that this is a known deficiency and it should be avoided.