Mod_ruby used to mimic rewrite

http://groups.google.com/group/comp.lang.ruby/browse_frm/thread/92e7ea6b723b8162/e128a087206d37b2?q=mimic+rewrite&rnum=1#e128a087206d37b2

This post subject made me wonder. I would like to get the effect of a
virtual host + apache rewrite instruction without actually changing
the apache.conf file

I was wondering if the information in this post, which I don't
understand indicates that
1. it is possilble
2. how to do it

I am learning web programming, I have erb, eruby, cgi, mod-ruby, nitro
and rails working in various directories. For now I would like to work
with mod-ruby with one routing file which would route each of the small
projects I will develop over the summer to the corresponding project
cgi controller file.

I know it can be done with virtual host and rewrite commands in the
apache conf file, but I don't like to touch Apache except for software
installations. Can mod_ruby mimic rewrite apache commands?