?? Comments begin with a ?
!insert "usage.gn".
!insert "math.gn".

!entrypoint <- main.

?? Type definitions begin with the name wrapped in ()
(add <- Int <- Int) -> Int.
add a b -> a + b.

(main) -> Int ? (effects -> IO).
?? Function definitions begin with the name and have an ->
main -> match (x <- println "Hello World") (
    (x >= 0) -> x,
    (x < 0)-> add x 10,
).