There are some major things missing in the UDL, and I'm actually quite disappointed with it. Currently, it is entirely impossible to set up a proper xml-based language, as using delimiters to define tags will automatically highlight anything between the open and close bracket.
To see what I mean, try making a UDL that can highlight this properly:
<text It's your bedroom, there's a bed and a desk with a lamp. Not much to do here./>
This is a language based on XML. <tags> should be highlighted one color, but the contents should be a separate color.
Also, I should be able to fold beginning with the begin tag and ending with the end tag of the same name, which is currently not possible.