Something like this perhaps?

foreach my $key1 (sort keys( %hash ) )
{
    foreach my $key2 (sort keys( %{$hash{$key1}} ) )
    {
        foreach my $key3 (sort keys( %{$hash{$key1}{$key2}} ) )
        {
        }
    }
}
[download]

PS: If it is not actually three levels deep, and you simply want to sort based on three different hash values, then you'll want to do something more like this:

@SortedArrayOfHashes = sort 
            { 
            return $a->{'key1'} cmp $b->{'key1'} or  # if these are eq
+ual try the comparison below
                    $a->{'key2'} cmp $b->{'key2'} or # if these are eq
+ual try below
                    $a->{'key3'} cmp $b->{'key3'} #if these are equal,
+ then we give up; they're the same.
            }
            @ArrayOfHashes;
[download]