sub ref_to_db {
  my $db = DBI->connect(...);
  return $db;
}

##</code><code>##

sub closenow {
  my $rDB = shift;
  my $DB = $$rDB;
  $DB->disconnect();
}

##</code><code>##

sub closeplease {
  my $Booga = shift;
  my $DB = ${$Booga->{DB}};
  $DB->disconnect();
}

##</code><code>##

sub closeitnow {
  my $rDB = shift;
  $rDB = $rDB->{DB} if ref $DB eq 'HASH';
  my $DB = $$rDB;
  $DB->disconnect();
  $rDB = undef; # now the caller's reference is gone, too!
}