my $error='';
sub _val
{
  my $self=shift;
  my $key=shift;
  if(@_)
  {
    $self->_error();
    my $val=shift;
    unless($self->{sonstwo}->set($key => $val))
    { $self->_error("Can't set $key => $val"); }
  }
  return $self->{sonstwo}->get($key);
}

sub ein_wert { shift->_val('ein_wert', @_); }
sub noch_ein_wert { shift->_val('noch_ein_wert', @_); }

sub _error { shift->{error}=shift//''; }

sub error{ref($_[0])?$_[0]->{error}:$error}