sub set {
  my ($self, $value, $field) = @_;
  $self->{$value} = $field;
}

sub update {
  my ($self) = @_;

  $self->set('feld1', 'wert1');
  $self->set('feld2', 'wert2');
  $self->set('feld3', 'wert3');
}