Add tests for subs on multi-dim arrays.
Add tests for subs on multi-dim arrays.

To complement the methods tests, and make sure we don't have any
divergences in behavior. (We do, as noted in RT #126799, in reverse;
this is being patched. But this shows that in all the other cases we
are already doing the righ thting.)

dankogai/roast,dankogai/roast,skids/roast,bitrauser/roast,perl6/roast,dogbert17/roast,dogbert17/roast,zostay/roast,bitrauser/roast,b2gills/roast,b2gills/roast,dankogai/roast,skids/roast,b2gills/roast,zostay/roast,zostay/roast,skids/roast