use Test::More;

You are deliberating over what tool to use, but I would invite you to postpone that question and get busy writing a test suite.

What do you want your class to do? Have your test suite cover every interface method (including the constructor and the accessors), but above all convince yourself that a class that passes your tests will accomplish your goals.

I confess I find it hard to write tests when I really want to be coding the implementation, but I remind myself that

• tests are code too, and I enjoy writing them once I get started;
• coding the implementation is way more fun when I have a test suite in hand;
• managers asking after specs and documentation have been known to accept a well-commented test suite, or failing that, the test suite is a good outline for a requirements document.

Now you can safely pick a tool at random from among your favorite answers in this thread. You can even change your mind later and convert your classes to a different implementation. If your design is properly encapsulated, you'll be fine.

That said, I do have my own preference for inside-out or flyweight implementations. I think building classes in this way is like use strict. It catches dangerous practices (in this case, accessing your object's internals directly) at an earlier stage of development.