Slap: Functional Concatenative Language with a Borrow Checker?

Borrow checker in a functional concatenative language is a wild combination. I write Rust for real-time audio and Elixir for the orchestration layer in the same project, so I deal with both worlds daily. In Rust the borrow checker saves you from data races but fights you on anything concurrent. In Elixir you just don't have shared mutable state at all, problem solved differently. Curious where Slap lands -- does it feel more like Rust's "prove to the compiler you're safe" or more like "the language just doesn't let you do the unsafe thing"?