Each of the following illustrate a nested REPEAT.
The first example is for a circle based on squares, the second for
Note that for the square the inner REPEAT means you move along six
sides. This seems redundant but it is a way to get the turtle to a
position which means it is ready to draw the next square.
A similar strategy has been applied to the hexagon pattern with
REPEAT 9 not REPEAT 6.
REPEAT 12 [REPEAT 6 [FD 30 RT 90]
REPEAT 8 [REPEAT 9 [FD 30 RT 60] LT