I was surprised to see that you could get "keys" for a scalar.

Then I RTFM, and found:

Starting with Perl 5.14, "keys" can take a scalar EXPR, which must contain a reference to an unblessed hash or array. The argument will be dereferenced automatically. This aspect of "keys" is considered highly experimental. The exact behaviour may change in a future version of Perl.

So - I would continue to code your last line as:

say "\t$_ => $inner->{$_}" for sort keys %$inner;
[download]

Which, to me, is safer and saner.