std::any an_object{ std::string("hello world") };
if (an_object.has_value()) {
    std::cout << std::any_cast<std::string>(an_object) << '\n';
}

try {
  std::any_cast<int>(an_object);
} catch(std::bad_any_cast&) {
    std::cout << "Wrong type\n";
}

std::any_cast<std::string&>(an_object) = "42";
std::cout << std::any_cast<std::string>(an_object) << '\n';

Output

hello world
Wrong type
42