msgpack

case erlang:system_info(otp_release) of

    %% Rxx, before R16
    [$R|_] ->
        HashDefine = [{d,without_map}],
        case lists:keysearch(erl_opts, 1, CONFIG) of
            {value, {erl_opts, Opts}} ->
                lists:keyreplace(erl_opts,1,CONFIG,{erl_opts,Opts++HashDefine});
            false ->
                CONFIG ++ [{erl_opts, HashDefine}]
        end;

    %% In 17, maps are experimental
    "17" ->
        CONFIG;

    _ ->
        HashDefine = [{d,default_map}],
        case lists:keysearch(erl_opts, 1, CONFIG) of
            {value, {erl_opts, Opts}} ->
                lists:keyreplace(erl_opts,1,CONFIG,{erl_opts,Opts++HashDefine});
            false ->
                CONFIG ++ [{erl_opts, HashDefine}]
        end
end.