ModelBusiness logic goes hereViewPresentation logic goes hereControllerApplication logic goes hereHere's a typical bit of "controller" logic: sub add_product_to_order {   my ( $dbh, $p_id, $o_id ) = @_;   unless ( $o_id && $o_id =~ /^\d+$/ ) {     dienice("Bad order number $o_id");   }   my $o_sql = 'SELECT * FROM orders  WHERE id = ?';   my $p_sql = 'SELECT * FROM products WHERE id


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