rem: end_tag = "</" >> fstr_p(element.tag) >> '>';
add: end_tag = "</" >> f_str_p(element.tag) >> '>';
context:         definition(tags const& /*self*/)        {            element = start_tag >> *element >> end_tag;            start_tag =                    '<'                >>  lexeme_d                    [                        (+alpha_p)                        [                            //  construct string from arg1 and arg2 lazily                            //  and assign to element.tag                            element.tag = construct_<string>(arg1, arg2)                        ]                    ]                >> '>';            end_tag = "</" >> fstr_p(element.tag) >> '>';        }