dovecot - Sep 2018 - [Sieve] How to retrieve part of message as a variable

I need to retrieve some parts of a message which looks like

Subject: Test message
Message-Id: <2788db2f-b5c3-4b8c-881e-362c3df4f915 at server.local>
Mime-Version: 1.0
Content-Type: multipart/report;
boundary="----=_Part_fba0c199dfcd4d60ae506b37a6320a84";
report-type=disposition-notification
To: adam at test.local
Date: Mon, 17 Sep 2018 16:21:45 -0400 (EDT)
From: postmaster at server.local


------=_Part_fba0c199dfcd4d60ae506b37a6320a84
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

BTW, this is the correct notification ... it should be "failed" not
"failure".
------=_Part_fba0c199dfcd4d60ae506b37a6320a84
Content-Type: message/notification
Content-Transfer-Encoding: 7bit

Final-Recipient: rfc822; eve at test.local
Original-Message-ID: <06dbfc12-57a5-49bd-84bd-a24bc3ba1e42 at
fake.cernerasp>

------=_Part_fba0c199dfcd4d60ae506b37a6320a84?

for an example I need to grab what is after ?Final-Recipient: rfc822;? and
?Original-Message-ID:? and store them as variables

Thanks
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