I'm gonna assume you're using MySQL 3.x, which I think doesn't have subqueries.

my $q_state          = $dbh->quote($state);
my $q_status         = $dbh->quote($status);
my $q_comment_status = $dbh->quote($comment_status);


my $stmt1_where = "";
$stmt1_where .= " AND Speedtrap.state=$q_state\n"
   if ($state && $state ne 'all');
$stmt1_where .= " AND Speedtrap.approval=$q_status\n"
   if ($status && $status ne 'all');
$stmt1_where .= " AND Comments.approval=$q_comment_status\n"
   if ($comment_status && $comment_status ne 'all');
$stmt1_where .= "\n";

my $stmt1 = <<";";
SELECT DISTINCT
       Speedtrap.id,
       Speedtrap.state,
       Speedtrap.city,
       Speedtrap.discription,
       Speedtrap.approval,
  FROM Speedtrap
  LEFT JOIN Comments
    ON Speedtrap.id = Comments.id
 WHERE 1=1
$stmt1_where
 ORDER BY $sort $sortord
;


my $stmt2_where = "";
$stmt2_where .= " AND Comments.approval=$q_comment_status\n"
   if ($comment_status && $comment_status ne 'all');
$stmt2_where .= "\n";

my $stmt2 = <<";";
SELECT COUNT(*) AS num_comments
  FROM Comments
 WHERE Comments.id = ?
$stmt2_where
 ORDER BY $sort $sortord
;


my $sth1 = $dbh->prepare($stmt1)
|| die("...: $DBI::errstr\n");

my $sth2 = $dbh->prepare($stmt2);
|| die("...: $DBI::errstr\n");

$sth1->execute()
or die("...: $DBI::errstr\n");


...[ print start of page ]...

while (@row = $sth1->fetchrow_array()) {
   my ($id, $state, $city, $desc, $approval) = @row;

   $sth2->execute($id)
   or die("...: $DBI::errstr\n");

   # Should always return exactly one record.
   my ($comment_count) = $sth2->fetchrow_array();

   ...[ print repeated part ]...
}

...[ print bottom of page ]...


$sth2->finish();
$sth1->finish();
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