[geoffhill]

Racket supports running multiple (sometimes incompatible) dialects of Scheme through the use of a #lang directive.

If you prefix your program with "#lang racket", you get the definitions for the full Racket language, with all of the extensions and libraries that Racket provides.

But if you want to preserve compatibility with the standard and with other implementations, you can prefix your program with "#lang r5rs". It derives from the same base language as Racket.

http://docs.racket-lang.org/r5rs/r5rs-mod.html