# is there any way to limit the scope of bless?
sub doit {
  my $db = shift;
  die "not a database class: $db" unless $db->isa("Database");

  my $original = ref($db);
  bless $db, "Database::Special";
  $db->doSomethingSpecial();

  bless $db, $original;
  return $db->doNormalStuff();
}