In order to verify that a string matches a regular expression, perform the following steps:

1. Include headers <regex> and <string> and the namespace std::string_literals for C++14 standard user-defined literals for strings:

        #include <regex> 
        #include <string> 
        using namespace std::string_literals;

2. Use raw string literals to specify the regular expression to avoid escaping backslashes (that can occur frequently). The following regular expression validates most e-mails formats:

        auto pattern {R"(^[A-Z0-9._%+-]+@[A-Z0-9.-]+.[A-Z]{2,}$)"s};

3. Create an std::regex/std::wregex object (depending on the character set that is used) to encapsulate the regular expression:

        auto rx = std::regex{pattern};

4. To ignore casing or specify other parsing options, use an overloaded constructor that has an extra parameter for regular expression flags:

        auto rx = std::regex{pattern, std::regex_constants::icase}; 

5. Use std::regex_match() to match the regular expression to an entire string:

        auto valid = std::regex_match("[email protected]"s, rx);