sub get_group {
  my ($dbh, $group) = @_;
  my $sth = $dbh->prepare(
    "SELECT username, password, group FROM users
     WHERE group = ?");
  $sth->execute($group)
    or warn "Can't select on group: $DBI::errstr\n";

  my @users = ();
  while( my $user = $sth->fetchrow_hashref()) {
    push @users, $user;
  }
  return @users;
}