Applescript/Mail rule needed to forward copies of emails

I am using Mail 8.1, under Yosemite (MacOSX 10.10).

I am receiving emails into a Mailbox called “Responsesin” used only for this explicit purpose, each of which has as its Subject a valid email address.

What I would like to do is have a Rule that

(1) sends a copy of each email to the email address that is its Subject, with the following changes:

(2) the Subject of the sent email is changed to “Response via

(3) text of “abcdef” within the body of the email gets changed to “xyz”

(4) text of “ABCD” gets added to the beginning of the body of the email

I am fairly sure that this cannot be achieved using only Mail Rules, and so assume that the best way is to have an Applescript to achieve the steps above, and have that called whenever a Mail Rule detects that a new email has arrived in “Responsesin”.

My intention is that “Responsesin” gradually fills with emails, which I can keep as long as I wish, secure in the knowledge that each one has been forwarded to the recipient identified by the Subject line.

Thank you if you can help me with this.