Perl CSV to Access- IF RECORD DOESNT EXIST

The code below works correctly and inserts values from the CSV file into the Access Database. How do I adjust the script to check and see if the record from the CSV file already exists in the database?

I do not want to import duplicate records. Thanks.

use DBI;

$fhour="00";
$count=0;
$finterval=12;

do {

$csvfile="C:/WeatherModel/degrib/bin/Model/Output/gfs_2010111900_" . $fhour. ".csv";

$dbh = DBI->connect('dbi:ODBC:driver=Microsoft Access Driver (*.mdb);dbq=c:/weathermodel/weathermodel.mdb', '', '');
$sth = $dbh->prepare( "INSERT INTO GFS_Forecasts VALUES (?,?,?,?,?,?)" );

open CSV, $csvfile;


$x=0;
while(<CSV>) {


if ($x>0){
	  chomp;
  my @fields = split /,/;	

  $sth->execute(@fields);
}
$x++;

}

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