For example, if I have a site http://www.example.com/, I might want
all visitors to http://example.com/ to redirect to http://www.example.com/
(or vice versa). This is recommended for SEO purposes to help prevent
duplicate content being detected. Normally you'd use a rewrite rule
with a host-based condition to deal with this, but is there a way of
doing it without activating mod_rewrite?

I could always activate mod_rewrite and deal with it the classic way,
but since it's hinted that this isn't a Good Thing (tm) to do, I'd
like to avoid doing that.