Concrete language comparisons?

[Adam Chlipala]

Here's an idea for structuring some sessions, based on a (hopefully not
too large) amount of work done ahead of time:

Can we identify a few "challenge problems" that can be implemented in
different languages, providing an opportunity for a concrete comparison
of pros and cons? Presenters and others could build solutions ahead of
time and perhaps spend some time presenting them. We could have
solutions both in the "emerging" languages and in more established
languages.

I'm especially interested in code reuse in Web applications. I'd like
to see some attempts at building libraries that make it easy to create
applications in specific domains.