I have an app where the shortened “preview” can be supplied by the article author or editor

The code in the question was significantly cut down to get to the core of the problem. In the actual implementation, there are two blocks of text. One is a preview and the other is the main text. It is the preview that we need to be able to toggle between just an extract and the full copy. Although even here I missed a bit out. The creator of the text can add a <split> tag to control where the block of text is split. In reality, this is not often used but it will remain in the refactored, templated code.

Thanks for sharing - that gives me more food for thought.