my $dbh = DBI->connect ("dbi:$driver:", "user", "pass", { FetchHashKeyName => "NAME_lc" });
my %hash;
my $sth = $db->prepare ("select week, month, workperiod from tablename");
$sth->execute;
while (my $rec = $sth->fetchrow_hashref) {
    $hash{$rec->{week}} = [ $rec->{month}, $rec->{workperiod} ];
    }