playing nice with non-moose classes

so,

i'm trying out moose for some real work for the first time. i'm not  
entirely clear on one thing.
if i want to have an attribute that is an instance of a class that  
isnt a moose class, is this all
i have to do

use NotMooseClass;

has 'not_moose' => ( is => 'rw', isa => 'NotMooseClass' );

i'm 99% certain that is right BUT... if it isn't i'm obviously missing  
something basic so i figured,
best to ask first because, if i got that wrong, lord knows what else  
i'm getting wrong.