itās a recent change (was only added in 3.0). this allows to simplify doing something like this:
L 1 4: SCRIPT 5 where you need to use the current iteration number in the called script, before you had to use a global variable to pass it in: L 1 4: A I; SCRIPT 5.
not sure itāll work for recursive purpose though, if you call a script from itself it wonāt restore the previous I value once it returns.
this would require a separate set of ops, similar to pattern ops, where the turtle number would be one of the parameters.