G'day bliako,

++ Thanks for taking the trouble to dig out that old (2004) post.

The text regarding rotations from zentara (which you've quoted) actually refers to Tk::Zinc; rotations are not possible with Tk::Canvas. From "Tk::Canvas - TRANSFORMATIONS":

... Canvases do not support scaling or rotation of the canvas coordinate system relative to the window coordinate system.

Individual items may be moved or scaled using methods described below, but they may not be rotated.

The thinking behind your guess is valid; unfortunately, it cannot work.

That's a pity because it would have been useful. For instance, rotating the bend through 90° clockwise, could have made the creek flow north, instead of south, without the need to code a separate group. Presumably, had that been possible, the [0, 0] would have needed to be [50, 50] to rotate about the centre.