Here's how I did it (assuming I pasted the relevant stuff correctly :).

$tmpl->param('loop' => db_get_loop());


sub db_get_loop {
        my ($dbh, $sql, $sth, @loop_info, $limit,
                $last_update, $city, $zipcode, $name,
                $low, $high, $date, $forecast,
                $forecast_description);

        $dbh = db_connect();

        $sql = qq{SELECT last_update,city,zipcode,name,low,high,
                                date,forecast,forecast_description
                          FROM $TABLE
                          ORDER BY last_update DESC, date
                          LIMIT $limit};
        $sth = $dbh->prepare($sql);
        $sth->execute();
        $sth->bind_columns(\($last_update, $city, $zipcode, $name,
                                           $low, $high, $date,
                                           $forecast, $forecast_descri
+ption));
        while ($sth->fetchrow_arrayref()) {
                my (%loop);

                # Set TMPL_VARs for each iteration
                # in the <TMPL_LOOP NAME="${region}_headlines_loop"> l
+oop
                $loop{'last_update'} = $last_update;
                $loop{'city'} = $city;
                $loop{'zipcode'} = $zipcode;
                $loop{'name'} = $name;
                $loop{'low'} = $low;
                $loop{'high'} = $high;
                $loop{'date'} = $date;
                $loop{'forecast'} = sprintf('%02d', $forecast);
                $loop{'forecast_description'} = $forecast_description;

                # Push this row onto loop
                push @loop_info, \%loop;
        }
        $sth->finish();
        $dbh->disconnect();

        return \@loop_info;
}
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You could put all those variables in a hash, instead. That's just how I happened to do it.