This is not a real script, it is a script used for testing of syntax description PowerShell.hrc for Colorer and covering related issues. Perhaps this HTML looks like a Christmas Tree, no problem, it is just a demo. One can configure Colorer according to his preferences. Take a look at how it handles and distinguishes expandable and not expandable string content and escaping rules, is not it a beauty?
EDIT: replaced large demo text with a link