[gosub]

While CL and scheme are both lisp dialects, they are quite different. Just to make a pair of examples, CL has two separate namespaces for variables and functions, scheme only one; scheme has guaranteed tail call optimization (which is used often to solve problems recursively), CL depends on implementations. To do these koans I would first go through Practical Common Lisp by Seibel http://www.gigamonkeys.com/book/

[brudgers]

The optimization of tail-call optimization is converting some recursive procedure descriptions into iterative processes. A recursive procedure description may instead describe a necessarily recursive process. The difference between descriptions and the procedures they produce is one of the issues covered in SICP - most explicitly by Ableson in one of the videos.