code: func IsCIdentifier(value string) []string {
  	if !cIdentifierRegexp.MatchString(value) {
  		return []string{RegexError(identifierErrMsg, cIdentifierFmt, "my_name", "MY_NAME", "MyName")}
  	}
  	return nil
  }
docs: // IsCIdentifier tests for a string that conforms the definition of an identifier
  // in C. This checks the format, but not the length.