In MgrCompanyLink.pm (which has fields id, company and manager):
WebApp::MgrCompanyLink->has_a(company => 'WebApp::Company');
WebApp::MgrCompanyLink->has_a(manager => 'WebApp::Manager');

In Manager.pm (which has fields id and person):
WebApp::Manager->has_a(person => 'WebApp::Person');
WebApp::Manager->has_many('companies',
			[ 'WebApp::MgrCompanyLink' => 'companyid'],
			'mgrid',
			{ order_by => 'companyid' }
			 );