my $sum1= Variable->new( "first_summand" );
my $sum2= Variable->new( "second_summand" );
my $sum3= Variable->new( "result" );
my $adder= Addierer->new();
$adder->connectFirstSummand( $sum1 );
$adder->connectSecondSummand( $sum2 );
$adder->connectResult( $sum3 );

$sum1->setValue( 5 );
$sum2->setValue( 3 );
print $sum3->getValue(); # should print 8