In Class::DBI we declare these table relationships in our Class:
package FilmBuff::DBI;
use base 'Class::DBI';
FilmBuff::DBI->set_db('Main', 'dbi:mysql:database=test', 'test', '');
# FilmBuff::Person
package FilmBuff::Person;
use base 'FilmBuff::DBI';
FilmBuff::Person->table('person');
FilmBuff::Person->columns('id', 'name');
FilmBuff::Person->columns(Primary => 'id');