# if someone calls B, the call should be forwarded to C too.
   if (method=="INVITE" && uri=~"sip:B@xx.xxx.xx ")
   {
       # copy the current branch (branches[0]) into
       # a new branch (branches[1])
       append_branch();
       # all URI manipulation functions work on branches[0]
       # thus, URI manipulation does not touch the 
       # appended branch (branches[1])
       seturi("sip:C@domain");
       # now: branch 0 = C@domain
       #      branch 1 = B@xx.xx.xx.xx