sub check_exist {
  $username = shift;
  # do the necessary dbi conection...
  $sql = qq{ SELECT * FROM $table{'members'} WHERE nick="$username"};
  $sth = $dbh->prepare($sql);
  my $result = $sth->execute()
	or bail_out("Cannot execute query.");
  $dbh->disconnect();
  if ($result eq '0E0') {
    return $username;
  }
  else {
    bail_out("$username has already been taken...");
  }
}