package BaseItem;

sub moveto ($$$$) {
  my $self  = shift;
  my $new_x = shift;
  my $new_y = shift;
  my $new_z = shift;
...
}

sub position ($) {
  my $self  = shift;
  return ($self->{x}, $self->{y}, $self->{z});
}

...

##</code><code>##

package Item;

our @ISA = qw(BaseItem);

...