thanks all of you.. i finally sorted it out.. i changed the function to this and it works

if($prodid && $cat_featureid && $value){
    my $sql = "INSERT INTO products_features (product_id, feature_id, 
+value) 
        VALUES (".$prodid.", ".$cat_featureid.", ".$dbh->quote($value)
+.") 
        ON DUPLICATE KEY UPDATE value=".$dbh->quote($value);
    
    $dbh->do($sql);
}
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