PL/SQL function: raise exceptions and fill in output variables

If we use "x_out_param OUT VARCHAR2", and an exception is raised in the function, the parameter won't be filled in.
The trick consists in using the NOCOPY keyword to pass variables by reference and not by copy.

PROCEDURE PROC(x_out_param OUT NOCOPY VARCHAR2) IS
BEGIN
    ...
    x_out_param := 'some value';
    RAISE MY_ERROR_EXCEPTION;
END PROC;

PROCEDURE MAIN(x_out_param OUT VARCHAR2) IS
BEGIN
    ...
    PROC(x_out_param);
EXCEPTION
    WHEN MY_ERROR_EXCEPTION THEN RETURN 1;
    WHEN OTHERS THEN RETURN 2;
END MAIN;