I don't really understand calling Perl declarative... I would consider the Perl CGI services I used to work on to be quite a bit more imperative than the Rails applications I've worked on. Similar with PHP, though I can see where peppering the imperative code into the declarative HTML could be considered more declarative.

Yeah, sorry, Perl is probably a bad example (I was really thinking of Mason, and even then it's a bad example). Pulled that from the list!

There's nothing declarative about HTML except for its extremely limited use case of rendering text.

HTML is purely declarative.

Each HTML document describes what it wants to have rendered, but does not describe how it should be rendered.

In theory, maybe. In practice, no. I've been round and round on ADA issues, and there is no clear distinction between "meaning" and "presentation". Clean separation is either a pipe dream, or too complex for most mortals to get right. I should become an ADA lawyer because I can now pop the purists' BS and win case$.