rlm_perl DEBUG log with garbage output

Hi,.. running xlat within rlm_perl.. giving correct result.. but what concern me is that.. in debug log.. there are garbage output as below:- radius_xlat: '.*' radius_xlat: Running registered xlat function of module y5perl for string '%{User-Name}:%{NAS-Identifier}' radius_xlat: 'bacang:JARINGWiF' rlm_perl: Len is 4 , out is NULL?8???Ù¿¿?49(hÕ¿¿?? freespace is 254 radius_xlat: 'NULL' calling from :- attr_rewrite wifi { ##some code replacewith = %{y5perl:%{User-Name}:%{NAS-Identifier}} } preacct { y5perl wifi files } sub xlat { # some code # return NULL or "somevalue" return ($value); }