Reference

     (array, variable) A special value that refers indirectly to a variable
     or array.  If one variable contains a reference to a second variable
     (achieved by passing the second variable by reference in a function or
     procedure call), operations on the first variable (including assignment)
     are passed through to the second variable.  If a variable contains a
     reference to an array, the elements of the array can be accessed by
     applying a subscript to the variable.