It's not strictly a programming language, but Scribble (a Racket language) is really the first document creation language that neither feels like a markup language with a programming language API nor a programming language with a document creation API. With this sort of setup, it is really easy to introduce arbitrary new constructs to avoid duplication or to better structure your document.

LaTex is the only system I know that comes close to this, but the language is pretty horrible to actually try and use (to be fair, LaTex has quite a bit of legacy it has to maintain).