Seems like Matthew is bored or is tired of all the questions he gets asked regarding Zend_Forms. A few days ago, he was posted this and now he has this:
You may have noticed in the previous installment that the decorator’s render() method takes a single argument, $content. This is expected to be a string. render() will then take this string and decide to either replace it, append to it, or prepend it. This allows you to have a chain of decorators — which allows you to create decorators that render only a subset of the element’s metadata, and then layer these decorators to build the full markup for the element.