dealing with misaddressed mail

I have my own vanity domain, and it is similar to a lot of other 
domain names. As a result, I get a lot of mail meant for people at 
one of those other domains.
My wife and I also use a few aliases for legitimate e-mail, and we 
have a couple of pop boxes.
What I want to do is let e-mail to legit aliases pass through, and 
bounce the clearly misaddressed e-mail with a note saying "you may 
have meant one of these other domain names."
I could define a separate recipe for each legitimate alias, and then 
have a recipe that is activated if none of the previous ones are, but 
I'm wondering if that is the most efficient approach. It would seem 
to be more elegant if I could do something like this (badly-formed 
pseudo-code follows):
alias1 = "aliasA, aliasB, aliasC"
alias2 = "aliasX, aliasY, aliasZ"

:0
{
:0
* TO_alias1
# Here, To would match any of the items in alias1 against
# any of the "To_" lines.
! realaddress1(_at_)crossroads(_dot_)net

:0
* TO_alias2
! realaddress2(_at_)crossroads(_dot_)net
}

:0 E
(send reply cat'ing error message in a text file to sender's original message)

thanks in advance,

   Adam Rice | adamrice(_at_)crossroads(_dot_)net
Austin TX USA | http://www.crossroads.net/