unpack

["Robert Ward" <r.ward@...>]

Hi,
I was puzzled by the results of unpack, below
> x = {'a', 'b', 'c', 'd', 'e'}
> y = {'v', 'w', 'x', 'y', 'z'}
> print(unpack(x), unpack(y))
--> a       v       w       x       y       z

Since unpack returns all the table elements, I was expecting to see 
a   b   c   d   e   v   w   x   y   z

Is there a simple explanation of the principle at work here?
Thanks!