sub AUTOLOAD {
  my $self=shift;
  my $attr=$AUTOLOAD;
  unless (exists $allowed_attrs{$attr}) die "Hey, that attribute does not exist!\n";
  # %allowed_attrs lists the attributes you are allowed to access
  unless (exists $self->{$attr}) do_get_the_value_from_db(); # do_... would get the value and store it in $self->{$attr};
  return $self->{$attr};
}