Block a user
Empty blocks should cause parsing or validation errors
Validator should not allow re-binding of function parameters
home!
should reset orientation, not just location
Better error message: "mismatched arity" -> "wrong number of arguments"
ref
-> box
all the way through the parser, interpreter
Turtle position should correctly report location in turtle coordinates
Splat patterns should show word/name bindings in
doc!
and match errors