header_checks help, please

[Janos Dohanics]

Hello,

I have been trying to edit the Subject: line using header_checks,
without success:

header_checks.pcre:

if /^From: (.*)<(.+)mydomain\.com\>$/i
/^Subject: (.*)$/i
    REPLACE Subject: some_string $1
endif

main.cf:

header_checks = pcre:/usr/local/etc/postfix/header_checks.pcre

Would you please correct the error?

-- 
Janos Dohanics