I like the example from perlfaq4:

Here we'll do a reverse numeric sort by value, and if 
two keys are identical, sort by length of key, and if 
that fails, by straight ASCII comparison of the keys 
(well, possibly modified by your locale -- see perllocale). 

@keys = sort {
    $hash{$b} <=> $hash{$a}
        ||
    length($b) <=> length($a)
        ||
    $a cmp $b
} keys %hash;
[download]

as our peers above have pointed out ($$a{$key}) does the work in your case, but the idea of or'ing with a final cmp will probably get better results when you can't tell what's in those arrays.

#!/home/bbq/bin/perl
# Trust no1!