---
    #define GREET Hello
    GREET!
    #
    #define DO_GREET GREET, World
    DO_GREET!
    #
    #define Hello Bye
    DO_GREET!
    #
    #define Bye Good bye
    DO_GREET!
    #
    #define Hello \Bye, \Bye
    DO_GREET!
    #
    #define Hello \Bye, Bye
    DO_GREET!
    #
    #define Hello Bye, \Bye
    DO_GREET!
    #
    #undef Hello
    #define World Universe
    DO_GREET!
    #
    #undef World
    #define Universe World
    DO_GREET!
    ---
    #undef GREET
    #undef DO_GREET
    #undef Hello
    #undef Bye
    #undef World
    #return