[Serusers] textops and branch route

hello, is it possible to modify the Request URI or the header fields in branch_route? If yes, why the textop functions: subst, subst_uri, replace, search, can not be used in branch_route? ********************************************************************** The information in this message is confidential and may be legally privileged. It is intended solely for the addressee. Access to this message by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, or distribution of the message, or any action or omission taken by you in reliance on it, is prohibited and may be unlawful. Please immediately contact the sender if you have received this message inerror. **********************************************************************