elsif ($choice eq "update")            # update shopping cart
{
    update_cart ($cart_ref,  param("quantity"));
    $page .= format_cart_html ($cart_ref, 1);
}

##</code><code>##

sub update_cart
{
my ($cart_ref, $item_id, $qty) = @_;

    update ($cart_ref->{$item_id}->{qty} = $qty);
}

##</code><code>##

sub update {
   # a bunch of code
}