My apologize to everyone I told that functional programming is declarative.

It's actually imperative. Thank you @AndSoWeCode for figuring that out. I spent the whole day thinking about it.

Lisp is imperative. It's just different way to define the exact data transformations, and that's quite imperative.

On the other hand, HTML, CSS, config files and markup languages are declarative.

But writing the imperative program which is configured with declarative configs seems like great idea. Consider Apache web server and others.