foreach my $key1 ( sort keys %hash){
    foreach my $key2 ( sort keys %{$hash{$key1}){
        foreach my $key2 ( sort keys %{$hash{$key1}{$key2} ){          
        }
   }
}

##</code><code>##

foreach my $key1 ( sort keys %hash){
    foreach my $key2 ( sort keys %{$hash{$key1}){
           my $key3 = $hash{$key1}{$key2};
           my $value = $hash{$key1}{$key2}{$key3};
    }     
}