1Def0 = case erlang:is_builtin(erlang, binary_to_integer, 1) andalso
2            erlang:is_builtin(erlang, binary_to_float, 1) of
3           true -> [];
4           false -> [{d, no_binary_to_whatever}]
5       end,
6Def1 = case erlang:is_builtin(erlang, is_map, 1) of
7           true -> [{d, maps_support}|Def0];
8           false -> Def0
9       end,
10Defs = case os:getenv("JSX_FORCE_MAPS") of
11           false -> Def1;
12           _ -> [{d, maps_always}|Def1]
13       end,
14lists:keystore(erl_opts, 1, CONFIG,
15               {erl_opts, proplists:get_value(erl_opts, CONFIG, []) ++ Defs}).
16