Template Engine

I was just wondering if anyone had any good advice or tutorials on building a simple template engine system. I am woking on a small project that I would like to distribute, and I would of course like to separate logic from html. I really just want to know the basics without caching. I am familiar with Smarty and PHPLib and FastTemplate and some others. But since I am going to be distributing the app, I would like it as portable and small/simple as possible. Those template systems are overkill for what I need. Really it does not even have to be a "Template system", I would just like to here your thoughts on how you may have accomplished separation of logic from output in a simple way. Thanks, George