Similarly, TeX bakes units into its syntax, but METAFONT (which is much more pleasant as a programming language in general) just has a production for <numeric token> <numeric variable> instead (yes, it has a very involved context-dependent grammar), though it gives up type checking because of that.
julia's parser (which is written in scheme!): https://github.com/JuliaLang/julia/blob/master/src/julia-par...