testing procedure for collection type out params in sll*plus

I have created one procedure which has 2 out parameters.

One is simple type while other out parameter is a table of number.

when i execute my procedure with bind variables. i get error in execution for collection type out parameter that bind variable is not declared.(SP2-0552)

declare
type num_array is table of number index by binary_integer;
var y num_array;
var x number;
begin
ess.INTL_PERDIEM_CAL_PKG.PER_DIEM_INTTRAVEL_VER2('63',:x,:y);
end;

SP2-0552: Bind variable "Y" not declared.

Also tried

declare
var y ess.INTL_PERDIEM_CAL_PKG.INDV_PERDIEM;