Hi, In the textops module doc (http://openser.org/docs/modules/1.0.x/textops.html#AEN124) there is an example that demonstrates how to replace URI in the header "To" with the message URI: # replace the uri in to: with the message uri (just an example) if ( subst('/^To:(.*)sip:[^@]*@[a-zA-Z0-9.]+(.*)$/t:\1\u\2/ig') ) {}; After I've fixed a small mistake (instead of /t: I put /To:) it worked. But I don't understand how does it work. It looks like "u" is substituted by URI from R-URI but I didn't find such core variable. Could somebody explain me? Thank you in advance, Leonid Fainshtein