Pops and returns the last value of the array, shortening the array by one element.
Returns the undefined value if the array is empty, although this may also happen at other times. If ARRAY is omitted, pops the @ARGV array in the main program, but the @_ array in subroutines, just like shift.
Starting with Perl 5.14, pop can take a scalar EXPR, which must hold a reference to an unblessed array. The argument will be dereferenced automatically. This aspect of pop is considered highly experimental. The exact behaviour may change in a future version of Perl.
To avoid confusing would-be users of your code who are running earlier versions of Perl with mysterious syntax errors, put this sort of thing at the top of your file to signal that your code will work only on Perls of a recent vintage:
use 5.014; # so push/pop/etc work on scalars (experimental)