perl function shift

The shift function in Perl is used to remove and return the first element from an array. It can also be used to remove multiple elements from the beginning of an array.

Here's an example of using shift to remove and return the first element of an array:

my @numbers = (1, 2, 3, 4, 5);
my $first_number = shift @numbers;

print "First number: $first_number\n";
print "Remaining numbers: @numbers\n";

In this example, an array @numbers is defined with five elements. The shift function is then called with @numbers as its argument, which removes the first element (1) from the array and assigns it to the scalar variable $first_number.

The value of $first_number (1) is then printed using print, followed by the remaining elements of @numbers (2, 3, 4, 5).

Here's an example of using shift to remove multiple elements from the beginning of an array:

my @numbers = (1, 2, 3, 4, 5);
my @first_three_numbers = splice @numbers, 0, 3;

print "First three numbers: @first_three_numbers\n";
print "Remaining numbers: @numbers\n";

In this example, an array @numbers is defined with five elements. The splice function is then called with @numbers as its first argument, 0 as its second argument (indicating the starting index), and 3 as its third argument (indicating the number of elements to remove).

The removed elements (1, 2, 3) are assigned to a new array @first_three_numbers using list assignment.

The values of @first_three_numbers (1, 2, 3) and the remaining elements of @numbers (4, 5) are then printed using print.

Note that using shift on an empty array will return undef. If you want to avoid this, you can use defined to check the return value:

my @empty_array = ();
my $first_element = shift @empty_array;

if (defined $first_element) {
    print "First element: $first_element\n";
} else {
    print "Array is empty\n";
}