Stick on prefix of URL parameter

Hello everyone,

I have a backend with two servers and need to balance requests based on a URL parameter. I successfully tried this configuration:

stick-table type string size 10k expire 30m peers my_peers
stick on url_param(my_param)

Unfortunately the parameter my_param consists of an UUID and another ID which changes during a session. So I have to use only the first 36 characters of my_param. How can I do this?

Thanks and best regards