Step 1: Specify the source and target databases using Class::DBI

Legacy database Class::DBI (version 2, using Class::DBI::mysql):

package Legacy::DBI;
use base 'Class::DBI::mysql';

__PACKAGE__->connection('dbi:mysql:legacy_games', 'user', 'password');

package Legacy::DBI::Game;
use base 'Legacy::DBI';
__PACKAGE__->set_up_table('games');
__PACKAGE__->has_a('game_genre' => 'Legacy::DBI::GameGenre');

package Legacy::DBI::GameGenre;
use base 'Legacy::DBI';

__PACKAGE__->set_up_table('game_genre');