Not sure if can be considered "serious", but one example could be ЭЛЬ-76 (https:...

		rytis on Oct 25, 2019 \| parent \| context \| favorite \| on: قلب: a non-ASCII programming language written in A... Not sure if can be considered "serious", but one example could be ЭЛЬ-76 (https://en.wikipedia.org/wiki/Эль-76). Sample code: https://ramlamyammambam.livejournal.com/211315.html, and some lecture notes: https://drive.google.com/file/d/0B2e6QHbfGLLMZ094QTZwVmJxMlE... (Russian)