I think something was missed, and maybe I missed it. It looks to me like this:

    var a = getData();
    if (a != null) {
      var b = getMoreData(a);
      if (b != null) {
         var c = getMoreData(b);
         if (c != null) {
            var d = getEvenMoreData(a, c)
            if (d != null) {
              print(d);
            }
         }
      }
    }

will only print on non-null, whereas this:

    do
      a <- getData
      b <- getMoreData a
      c <- getMoreData b
      d <- getEvenMoreData a c
      print d

will always print something.