Implement the following script

General information for the business: implement the attached linux script
Description of requirements/functionality: I tried to implement the solution showed here to add the "reply-to" header to the messages:

http://unix.stackexchange.com/questions/248107/adding-reply-to-header-for-simple-postfix-mailing-list

I had no joy.

When I add line
smtp_header_checks = pcre:/etc/postfix/header_checks.pcre

(with file /etc/postfix/header_checks.pcre create as suggested)

to file
/etc/postfix/main.cf

the only visible result I experience is that messages are forwarded with a big delay :(

Please show me how this trick works
Specific technologies required: postfix regex
OS requirements: Linux
Extra notes: