Something like this? (untested)

for my $bibkey (sort keys %bibliography) {
   my $entry = $bibliography{$bibkey};
   print "$bibkey:\n";

   for my $key (sort keys %$entry) {
      print "\t$key => ", $entry->{$key}, "\n";
   }
}
[download]

Alternatively, $Data::Dumper::Sortkeys = 1;