if (method=="INVITE") {
                if (!isflagset(26) && !isflagset(27))
                {
                        if ($tU=~"^[1-9][0-9][0-9]$")
                                {
                                xlog("L_INFO", "User number is 3 digits\n");
                                avp_printf("$avp(s:tou)", "$tU");
                                avp_printf("$avp(s:fru)", "$fU");
                                xlog("L_INFO", "The to user is $avp(s:tou) and from user is $avp(s:fru)\n");
                                avp_subst("$avp(s:fru)/$avp(s:prf)", "/^([1-9][0-9][0-9][0-9]).*/\1/");
                                xlog("L_INFO", "The prefix is $avp(s:prf)\n");
                                subst_user("/^(.*)$/$avp(s:prf)\1/");
                                xlog("L_INFO", "New user is $rU\n");
                                }
                        else if ($tU=~"^[1-9][0-9][0-9][0-9][0-9]$")
                                {
                                xlog("L_INFO", "User number is 5 digits\n");
                                avp_printf("$avp(s:tou)", "$tU");
                                avp_printf("$avp(s:fru)", "$fU");
                                xlog("L_INFO", "The to user is $avp(s:tou) and from user is $avp(s:fru)\n");
                                avp_subst("$avp(s:fru)/$avp(s:prf)", "/^([1-9][0-9]).*/\1/");
                                xlog("L_INFO", "The prefix is $avp(s:prf)\n");
                                subst_user("/^(.*)$/$avp(s:prf)\1/");
                                xlog("L_INFO", "New user is $rU\n");
                                };
                };