Postfix Filters and header_checks

[Dennis]

Anybody know how to get a filter to work with postfix?

Here is what I want..

main.cf:
header_checks=/etc/postfix/header_checks

header_checks:
/Match Something/  FILTER ??:??

All the documentation I find for the header_checks just says foo:bar
where I put ??:??.  I just want to execute a script with the mail as the
input and then have the mail delivered unaltered.  So what is foo:bar
supposed to really be?  The docs/man pages say it's
transport:destination but I'm having trouble figuring out how to make
transport:destination into path/args for my script.

Any thoughts?

Thanks.
Dennis