Circularity has nothing to do with whether "REF" or "SCALAR" is returned. "SCALAR" references can be dereferenced via ${ $ref }, exactly like "REF" references, which argues for not making that distinction. Code that is going to traverse from $sv to $$sv is often also code that will traverse from checking ref $av to checking ref $av->[0] and from checking ref $hv to checking ref $hv->{$key} and so can cycle infinitely for any of those cases.