[plt-scheme] url rewriting

L.S.,

Is it possible to implement url rewriting with the PLT Webserver?
I'd like to rewrite things like:

http://x.y.z/somepage.html

to

http://x.y.z/servlets/program?page=somepage

Preferably without seeing it at the outside; except when the servlet 
really becomes "active",
i.e. is used in a continuation style fashion to handle forms.

--Hans