If STAMPOVAL, its inputs, and the value TRUE are all enclosed in parentheses, the oval drawn is filled with the current pattern in the current pen color. If the turtle's pen state is PENDOWN, STAMPOVAL colors the area with the current pen color. If the pen state is PENERASE, STAMPOVAL colors the area with the current background color, thus erasing the form. If the pen state is PENREVERSE, STAMPOVAL colors the area with the complement of the current area color; for example, white turns to black, and green to red. If the turtle's pen state is PENUP, STAMPOVAL has no effect.

See also STAMPRECT.