package doublyLinkedList;

sub new {
    my ($class, @elements) = @_;	

    my $self = bless {
	start => undef,
    }, $class;
	
    $self->push(@elements);
    return $self;
}

sub push {
    my ($self, @elements) = @_;
    for my $element (@elements) {
	my $newNode = {
		element => $element,
		next => undef,
		prev => undef,
	}; # newNode becomes an anonymous hash ref.
        if(not defined $self->{start}) {
            $self->{start} = $newNode; # the list is empty, assign to start as is
        } else {
            $newNode->{next} = $self->{start};
            $self->{start}{prev} = $newNode;
            $self->{start} = $newNode; # else make the new node point to start and then assign new node as the new start of the list.
        }
    }
    return;
}