No keywords at all — structure alone disambiguates. Nothing is reserved in English, so the language itself is localizable.
Fibonacci.zero
// Structural recursion on the inductive type Nat.
fibonacci(Nat) -> Nat {
.zero: 0
.suc(m): m {
.zero: 1
.suc(k): add(fibonacci(m), fibonacci(k))
}
}
$ zero eval 'fibonacci(1000)'
4346655768693745643568852767504062580256466051737178040248172908953655417949051890403879840079255169295922593080322634775209689623239873322471161642996440906533187938298969649928516003704476137795166849228875 (209 digits)