For the last 6 months I've been building and using an open-source structured LLM prompting language called Metaphor. It has a prompt compiler that lets you use a modular approach to constructing LLM problems, rather like a normal programming language.

I, and some early adopters, have been using this for doing things like complex software design and document generation work. It's sort of the opposite of vibe-coding because this is much more about deliberate planning and iteration using AIs, including having AIs help with reviewing and improving the work that both they and the humans have done. It also helps build up the sort of documentation that's so important when you're building something complex you want other people to be able to work on too.

Metaphor prompts can be committed to source control, just like regular source files, and then reused as desired.

The latest version of the m6rc prompt compiler also lets you template parameters so you can build reusable AI tools just by describing the behaviour you want.