How do I search and capture text for use in a rule?

[Steve Dondley]

I want to extract the first part of an email address from the 
"Delivered-To" header and use it witin a custom rule.

Example pseudo code:
my ($first_part) = $email_file =~ /^Deliver-To: (.*)/;

body __LOCAL_AWKWARD_INTRO /hi $first_part/i


How can I do this in my .cf file?