let draw =
  () {
    case Dom.Canvas.fromDomElement(canvas) {
      Maybe::Just(el) =>
        {
          // Skewed rectangles
          el
          |> Canvas.transform(1, 0, 1.7, 1, 0, 0)
          |> Canvas.setFillStyle(CanvasFillStyle::String("gray"))
          |> Canvas.fillRect(40, 40, 50, 20)
          |> Canvas.fillRect(40, 90, 50, 20)
          // Non-skewed rectangles
          el
          |> Canvas.resetTransform()
          |> Canvas.setFillStyle(CanvasFillStyle::String("red"))
          |> Canvas.fillRect(40, 40, 50, 20)
          |> Canvas.fillRect(40, 90, 50, 20)
          ""
        }
      Maybe::Nothing =>
        ""
    }
  }
{
  await Timer.timeout(0)
  draw()
}
<canvas as canvas/>