if i have modparam("tm", "tw_append", "params:P-X=$avp(i:100);P-Y=$var(foo)") and assign null to both $avp(i:100) and $var(foo) before t_write_unix(), then P-Y is appended (with value 0), but P-X is not. in my opinion, also P-Y should not be appended, i.e., script variable value null should be treated the same way as pseudo variable null value. -- juha