In Perl, the prefixes of sv, av, and hv might be more recognizable. Well, at least for people who have seen discussions that touched on internals that used the standard (and ubiquitous) abbreviations that are used internally.
At least, I have sometimes used names like $sv_xml when I saw a value in calling out "this is a reference (of this type)" in the variable name.
But ar, hr, and sr aren't any more recognizable than ra, rh, and rs (probably worse because, especially hr and sr, they are too recognizable as something else). I think aref, href, and sref would work fine. But if I want a prefix half that long, I'm going with av, hv, and sv. :)