my $dbh = DBI -> connect ("DBI:$driver:database=$db;host=$host",
                              $user, $password,
                              {RaiseError => 1, PrintError => 0,
                               AutoCommit => 0, Taint      => 1})
              or die "Failed to connect: $DBI:errstr\n";
 
    ...

    eval {
        my $sth = $dbh -> prepare ($cmd);
        $dbh -> execute (@variables);
        while (my @row = $dbh -> fetchrow_array) {
            ... process @row ...
        }
        $dbh -> commit;
    };
    if ($@) {
        $dbh -> rollback;
        croak "Database query failed: $@";
    }