PENERASE turns the turtle's pen into an eraser. When the turtle moves, it appears to erase by drawing in the current background color.
To stop PENERASE, use PENDOWN, PENUP or SETPEN.
This is a PENERASE command example. Its executes "SETPC 2 (STAMPRECT 80 20 "TRUE) PENERASE FD 30" command.
? PENERASE FD 30