@commands = ( 
    sub { $_[0]->add_node('W1') },
    sub { $_[0]->add_node('W2') },
    sub { $_[0]->add_edge( W2 => 'W1' ) },
);

use GraphViz;
my $g = GraphViz->new();

foreach my $command (@commands) {
    $command->($g);
}