is_emptyniltrueis_emptyconsxlfalsehdconsxlxtlconsxlconsxlappendl1l2ifappendl1l2is_emptyl1ifappendl1l2truel2ifappendl1l2falseconshdl1appendtll1l2is_empty1nil0true0cons2false0hd1tl1append2ifappend3INNERMOST./TRS/Cime/append-wrong.trs