Modifying request-uri that can contain prefixes

Hello,

 

I am working on an HMR expression that reads a line till it finds a '+' and replaces it with '00', due to the number sometimes containing a variable length prefix this "+" can be either in the middle of the URI or at the beginning.

 

I have a working solution for when it is after the first 6 digits (a fixed length prefix), however this breaks when the "+" is at the beginning or the prefix changes length.

 

Ideally I would like some way of "searching" for the "+" symbol and saving the part before it and after it, then summing the result with the "00" inbetween. I also have issues with this prefix being added to anonymous URIs so the rule would need to be able to detect when this occurs and leave "anonymous" alone.