:: insert boilerplate about Why We Make You Do It Yourself ::
Oh, never mind, you've been around since 2002:
BEFORE your existing RewriteRule:
RewriteRule ^special http://www.example.com/message.html [R=302,L]
Here the R=302 is just a formality, since 302 (temporary) is the default value of [R], and the protocol-plus-domain makes your rewrite into a redirect regardless. But let's be precise about it.
That's assuming for the sake of discussion that you don't have a /dirname1/ or /dirnameblahblah/ that doesn't
need redirecting. If you do, fine-tune the condition to
Otherwise you don't need a closing anchor, since you're not capturing. But as long as we're here: the optimal domain-name-canonicalization rule has a single condition that looks like this
"exactly www.example.com or exactly nothing". That will also get rid of any incoming requests with appended port number. Psst!
I don't know exactly how long the post-editing cutoff is, but I'm sure it's more than two minutes ;)