my %quarternames = (1 => 'first',  2 => 'second', 3 => 'third', 4 => 'fourth');

my %tablenames = map { $_ => "$quarternames{$_}quarter" } 
                      keys %quarternames;

my %queries = map { $_ => " SELECT * FROM $tablenames{$_} WHERE 
                            userid = ? AND period = ? AND gradetype = ? " 
                  } keys %tablenames;

sub termgrades {
    my $period  = shift;
    my $quarter = shift;
    my $sth;
 
    return undef unless exists $queries{$quarter};
    $sth = $dbh->prepare_cached($queries{$quarter})
           or do { error ("2", "Could not prepare query for $quarternames{$quarter} quarter for $userdata[0]: $dbh->errstr");
                   return undef;
    };

    $sth->execute($userdata[0], $period, 2)
         or error("2", "Could not execute query for $quarternames{$quarter} quarter for $userdata[0]: $sth->errstr");
    return $sth;
}