You might want to take a look at how perlmacs:
http://john-edwin-tobey.org/perlmacs/
does it.  He links perl into emacs.  Here is part of the
description:
Emacs allows you to customize your environment using Lisp.
With Perlmacs, you can use Perl, too. This module allows Perl code
to call functions and access variables of Lisp.

regards,
-joe

> If that were possible, would there be benefits in converting
> Emacs to use Ruby instead of (e)lisp?  I'm thinking of:
> you'd get more readable code; it might be possible to
> integrate it tightly with other ruby code, and to C using
> Ruby's API.  Could it be faster (after tuning)?  Could
> the Ruby syntax mode be REALLY intelligent if you did it this
> way?