In search of cool Scheme

[Sam Tregar]

Hello all.  I need some cool Scheme.  I'd like to find a small Scheme
function or two that non-Scheme people might be easily impressed by.
Something to answer the question "Why Scheme?".  The non-Schemers I'm
targetting are Perl users, so no pattern-matching or text-munging is
allowed.  Perhaps someone has something that would be quite hard in Perl
but is easy in Scheme?  Maybe some complex tree manuevers or
self-modifying AI code?

I'd like to use this bit of code in the docs for my Perl interface to
Guile, Guile.pm, and later in its more friendly companion Inline::Guile.

Any ideas?
-sam