Erlang: replacing 'null' value with specified replacement in hieracy list tree

utility.erl

%% @doc replaces 'null' value with specified replacement in hieracy list tree
%% list elements can contain tuples
-spec replace_null(Replacement :: term(), InputTree :: list(), Accumulator :: list()) -> Result when
    Result :: list().
%% --------------------------------------------------------
%% manual testing : 
%%     > R = [[<<"username">>,<<"jid">>,<<"nick">>,<<"last">>,
%%               <<"subscription">>,<<"ask">>,<<"askmessage">>,<<"server">>,
%%               <<"subscribe">>,<<"type">>],
%%              [{<<"XXXXXXXXXXX">>,<<"AAAAAAAAAAA@im.domain.im">>,<<" ">>,
%%                <<"ZZZZZZZZZZZ">>,<<"B">>,<<"N">>,<<"  ">>,<<"N">>,null,
%%                <<"item">>},
%%               {<<"XXXXXXXXXXX">>,<<"BBBBBBBBBBB@im.domain.im">>,null,
%%                <<"CCCCCCCCCC">>,<<"B">>,<<"N">>,<<" ">>,<<"N">>,null,
%%                <<"item">>}]].
%%     > utility:replace_null(null, R, []) == R. 
%%       true  <-- the test result
%% --------------------------------------------------------
replace_null(_, [], A) -> lists:reverse(A); 
replace_null(R, [ null | T ], A) -> replace_null(R, T, [R | A]);
replace_null(Replacement, [H | T], A) when is_tuple(H) -> 
    R = replace_null(Replacement, tuple_to_list(H), []),
    replace_null(Replacement, T, [list_to_tuple(R) | A]);
replace_null(Replacement, [H | T], A) when is_list(H) -> 
    R = replace_null(Replacement, H, []),
    replace_null(Replacement, T, [R | A]);
replace_null(R, [H | T], A) when is_binary(H) ->  replace_null(R, T, [H | A]);
replace_null(_, _, A) -> A.