Salesforce API How to identify a Case from an email reference code Ref Ref

Question

1

I'm writing a Windows service that will poll my IMAP4 inbox for emails from clients and create new Cases in Salesforce based on them.

Sometimes emails come in with a Case reference code in the subject. Ex: "[ ref:00FFwxyz.500FFJJS5:ref ]". I'd like to assign such emails to the existing Case identified by the code rather than create a new one.

My questions is: Is there a definitive formula for extracting a unique Case identifier from the ref code?