gistfile1.txt

    package Builder;

    has input_data_provider => ( does => 'DataProvider' );
    has output_data_writer  => ( does => 'DataWriter' );

    sub new {

        # make a provider and accept

    }

    sub build {
        my $self = shift;

        while ( my $data = $self->input_data_provider->next ) {
            $self->output_data_writer->write_data($data);
        }
    }
}

# %params contains parameters for both the provider & writer
my $builder = Builder->new(%params);