Goal:
  
  A : Type
  H : ReflectEq A
  l1 : list A
  l2 : list A
  l : list A
  call := split_prefix l1 l2 : (list A * list A * list A)%type
  ============================
   (is_prefix l l1 → is_prefix l l2 → is_prefix l (fst (fst call)))


DEBUG:Going to execute:
lazymatch goal with
           | call:=?fp:_ |- _ => subst call; Init.funelim_constr fp
           end
DEBUG LTAC Evaluated term: (split_prefix l1 l2)