I just learned about Val today, but Rust has similar constraints. To write to a particular variable requires having ownership or a mutable reference, which only one part of the program can have at once. Since you can't have two mutable references in different parts of the program or in different threads, you need some sort of atomic encapsulating data structure to mediate access. Something like a mutex.

Newbies to Rust have a lot of trouble learning how to get the borrow-checker to accept their code, but what these restrictions are doing is syntactically ensuring there are no deadlocks or data races. It is presumably a similar story with Val.

If Val actually handles this differently, I'd love to know.