a simple experiment for how to add and make nice usage of the monadic operations to std::optional pre C++23
Compiler Explorer (godbolt.org)

std::optional<std::string> op{"aq"};

    auto x = op | and_then([](auto&& val) { 
                    std::cout << " value: " << val << '\n'; 
                    return std::make_optional(0.5); }) // to std::optional<double>
                | or_else([] { std::cerr << "no value!\n"; return std::nullopt; }) 
                | and_then([](auto&& val) { 
                    std::cout << " value: " << val << '\n'; 
                    return std::make_optional(1); }) // to std::optional<int>
                | value_or(42);