POP
===

syntax: (pop <place>)

This function removes the first element of an existing
list (The <place> must include a list). The removed
element will be returned as a number.

example:       >(setf list '(4 3 2 1))
               (4 3 2 1)
               >(pop list)
               4
               >list
               (3 2 1)