=over

=item shift ARRAY
X<shift>

=item shift EXPR

=item shift

Shifts the first value of the array off and returns it, shortening the
array by 1 and moving everything down.  If there are no elements in the
array, returns the undefined value.  If ARRAY is omitted, shifts the
C<@_> array within the lexical scope of subroutines and formats, and the
C<@ARGV> array outside a subroutine and also within the lexical scopes
established by the C<eval STRING>, C<BEGIN {}>, C<INIT {}>, C<CHECK {}>,
C<UNITCHECK {}> and C<END {}> constructs.

Starting with Perl 5.14, C<shift> can take a scalar EXPR, which must hold a
reference to an unblessed array.  The argument will be dereferenced
automatically.  This aspect of C<shift> is considered highly experimental.
The exact behaviour may change in a future version of Perl.

See also C<unshift>, C<push>, and C<pop>.  C<shift> and C<unshift> do the
same thing to the left end of an array that C<pop> and C<push> do to the
right end.

=back