Round corners for Openscad - Tutorial

I've been thinking on OpenScad libraries and tutorials of late, and in the process discovering more of what OpenScad can and can not do. Sometimes there are gems that I had not seen before, and I have a 'smack my forehead' aha moment.

This thing is a little bit of a tutorial on how to do rounded corners on things using the 'hull()' builtin module.

I derived from this other thing because although there is already a 'boxes.scad' that comes with the standard OpenScad, it shows that there's more than one way to skin a box.

The 'hull()' method basically fills out a convex hull based on the points that are layed out in 2D. In the case of a rectangle, you can essentially just place circles at the corners, and use the hull() with a linear_extrude(), and you've got your rounded rectangle thing.

module roundedRect(size, radius)
{
x = size[0];
y = size[1];
z = size[2];

linear_extrude(height=z)
hull()
{
// place 4 circles in the corners, with