A word of caution about *SL error messages. These messages are synthesized from fragments of sentences and then a global rewriter re-arranges them to improve their meaning based on work done by Guillaume Marceau, Kathi Fisler and Shriram (see SIGCSE 2010). The rewriter catches English phrases at the moment; you might be best off checking it out first.
Sorry -- one day we'll get this aspect right -- Matthias _________________________ Racket Developers list: http://lists.racket-lang.org/dev