pipe to a program with mysql virtual users

[Alejandro Vargas]

I am using postfix+mysql virtual domains/users+dovecot+sieve. I am
using virtual domains, users, and aliases in mysql. How can I create a
pipe to a program like "test: |/usr/local/bin/test". If I insert an a
record in aliases tables, postfix tries to deliver the mail to
"|/usr/local/bin/t...@mydomain.com" and passes the mail to dovecot
rejects it because it does not find it in the mailboxes table.