sub cards {
  # usage: $caller->cards([$cards])
  # $cards is an anonymous array of Card types
  # return: cards in pile

  my $self  = shift;
  if (@_) {
    $self->{cards} = shift;
    $self->num(int @{$self->{cards}});

    # From data dumping, it seems that I need this line
    for(@{$self->cards()}) { $_->where($self) }
  }
  return $self->{cards};
}