[SR-Users] Operations With Variables $var- does it need to load a module

[Omar]

In Kamailio 1.4.3

I have the following scenario:

$var(a) = 0
$var(b) = 0
$var(a) = $(tU{s.len});
$var(b) =  $var(a) - 5;

xlog(" $var(b)");

the result $var(b)  is always the same as $var(a)

should i check if some specific module is loaded?
the debugs does not show any error, and $var(a) and $var(b) are unique.

Variables are working, but not the operations with the variables.

regards

O