package Xyz ;
use strict ;
use warnings ;
use Class::Trait 'base' ;

package Xyz::XML ;
use base qw(Xyz) ;

sub render {
   print "test render XML" ;
}

package Xyz::YAML ;
...... etc

##</code><code>##

use Xyz ;
Xyz::XML->render() ; # this works
Class::Trait->apply($my_obj, 'Xyz::XML') ; # problems

##</code><code>##

test render XML
Trait (Xyz::XML) could not be found : Can't locate Xyz/XML.pm ......