roll over nested arrays

```apl
?3⍴⊂2 3⍴10

┌─────┬─────┬─────┐
│1 5 4│0 1 5│9 8 5│
│8 6 6│9 2 2│9 2 6│
└─────┴─────┴─────┘
```

```lisp
(april-f "?3⍴⊂2 3⍴10")

The right argument to ? can only contain non-negative integers or floats.
   [Condition of type SIMPLE-ERROR]
```

though you can force the broadcast with
```apl
?¨3 ⍴ ⊂10 10 ⍴ 255
```