I've built something similar but a completely new programming language with backtracking as the major feature. The intended use is dynamic OS configuration especially network interface configuration.

The interpreter is single-threaded but there is simple concurrency between the "processes", that is a process yields when it has nothing more to immediately do.

Old online demo build through Emscripten (it misses many new features such as functions): https://rawgit.com/ambrop72/badvpn-googlecode-export/wiki/em...

Docs currently still dying on Google Code archive: https://code.google.com/archive/p/badvpn/wikis/NCD.wiki

Source: https://github.com/ambrop72/badvpn