Pops and returns the last value of the array, shortening the array by one element. Has an effect similar to
- $ARRAY[$#ARRAY--]
 
If there are no elements in the array, returns the undefined value
(although this may happen at other times as well).  If ARRAY is
omitted, pops the @ARGV
 array in the main program, and the @_
array in subroutines, just like shift.