How to bind a C++ function to lua that return multiple values with luabind?

How to bind a C++ function to lua that return multiple values with luabind?

It is possible, using luabind, to bind the following function?
void retByRef(int &a, int& b) {
a = 10; b = 10
}
I was trying the following, but it is only working with functions that has
one parameter
def("retByRef", &retByRef, pure_out_value(_1))
There is way to specify a policy for each parameter?