Overloading Operators - C++

Question

I was experimenting with new overloaded operators, I have created one void operator and another one that returns something when it's called:

#include <iostream>

struct chichachicha{
    int operator()(){
        return 25;
    };
};

struct boomboom{
    void operator()() {
        std::cout << "Hi folks!" << std::endl;
    };
};

int main(){
    chichachicha objC;
    int f = objC();
    std::cout << f << std::endl;
    boomboom objB;
    objB();
    return(0);
}

Is this the best way to write a code that does that?

How can I write an operator that can be called from anywhere in the code without instantiating the associated struct, that returns void/nothing and only prints a string of text? I'm not considering static methods, just operators.