gistfile1.hrl

swap(Bin, Original, New) ->
    swap(Bin, erlang:byte_size(Original), Bin, Original, New, 0).

swap(BinOrig, OriginalLen, Bin, Original, New, Acc) ->
    case Bin of
        <<Original:OriginalLen/binary, Right/binary>> ->
            OtherRepl = swap(Right, Original, New),
            <<Left:Acc/binary,_/binary>> = BinOrig,
            <<Left/binary, New/binary, OtherRepl/binary>>;
       
        <<_:8, Other/binary>> ->
            swap(BinOrig, OriginalLen, Other, Original, New, Acc+1);
       
        <<>> ->
            BinOrig
    end.