So you are saying is to do the load of the CSV to the DB and the prepare once, and just execute the queries for each value in the hash? using placeholders? Like:

$sth = $dbh->prepare( " SELECT * FROM csvtable WHERE SITE LIKE ? AND H
+OUR = ? " ); 
foreach my $key (keys %cell_peakhr)
    {
      $sth->execute( $key, $cell_peakhr{$key});
      @db_result = $sth->fetchrow_array()
      if (scalar(@db_result) < 1)
        {
            $db_result[0] = $date;
        $db_result[1] = $cell_peakhr{$key};
        $db_result[2] = $key;
             foreach my $count (3..$row_size-1)
            {
                $db_result[$count] = "-";            
            }#foreach
        }#if
        print OUT join(',',@db_result)."\n";
    }
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