Structured Prompt Language / PromptQL

Hi all!
An idle question:
It hit me today that “prompt engineering” points at the lack of a structured language for how text works as an input into SD, whose affordances are discoverable.
One step is just to experiment with the tokenizer (like, could a language take interpolations in the input string, like “a painting of a {cat:.8, dog:.2} in the style of Picasso”
I just wonder if anyone has seen any research on say, “structured prompt languages,” or a kind of “PromptQL.” It occurs to me like databases have SQL, surely there are better ways of syntactically organizing prompts into SD.