But e.g. ml-family languages (like OCaml, F#, Haskell) and Rust just have the *if* expression that has a non-void value. If your language accepts expressions as statements (most do?), then I think that should just be compatible out of the box.
Oh, and Lua most famously does not accept expressions as statements. Which, now that I think of it, would actually evade most of the parsing complications.