I'd suggest concentrating on references. They are more general and more fundamental than objects. The idioms of "pass by reference" vs "pass by value" and the related issues of aliasing vs deep copying are of prime importance in any serious programming environment.

Object oriented programming is a very useful technique, but it's not the only such useful concept. That objects in perl are implemented as references to data structures is good for motivation, but facility with references is more important, in my opinion.

After Compline,
Zaxo