Each of the following illustrate a nested REPEAT. The first example is for a circle based on squares, the second for hexagons. 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.
to SQSP
REPEAT 12 [REPEAT 6 [FD 30 RT 90] LT 150]
end
and
to HESP
REPEAT 8 [REPEAT 9 [FD 30 RT 60] LT 135]
end