[SR-Users] Kamailio V4.2.5 append prefix to Request Uri problem.

[Yasin CANER]

Hello;
     i try to append prefix to  $rU like below in Kamailio V4.2.5 . i 
get error even if i set string value. it works only when i append like 
that $rU="3002"+$rU;

--------- 1 test------------
$var(prefix)=$avp(s:69);
$rU=$var(prefix)+$rU;
-FAILED
---------2 test ------------
$rU=$avp(s:69)+$rU;
-FAILED
------- 3 test ------------
$rU=$avp(i:69)+$rU;
-FAILED
-------ERROR---------
May 29 12:06:57 group1-imslab11 /usr/local/sbin/kamailio[26196]: ERROR: 
pv [pv_core.c:2115]: pv_set_ruri_user(): str value required to set R-URI 
user
May 29 12:06:57 group1-imslab11 /usr/local/sbin/kamailio[26196]: ERROR: 
<core> [lvalue.c:363]: lval_pvar_assign(): setting pvar failed
May 29 12:06:57 group1-imslab11 /usr/local/sbin/kamailio[26196]: ERROR: 
<core> [lvalue.c:416]: lval_assign(): assignment failed at pos: 
(790,7-790,22)

     it work on Version 4.1.7 like below correctly;
     $rU=$avp(i:69)+$rU;


Thanks

Yasin