Goal:
    A : Type  H : ReflectEq A  l2 : list A  l : list A
  ============================
   (is_prefix l []
    → is_prefix l l2 → is_prefix l (fst (fst (split_prefix [] l2))))


DEBUG:Going to execute:
move  =>/is_prefix_nil -> _
Level 2: evaluation returns
idtac
where
c := split_prefix l1 l2
of type
constr of type tacvalue

Level 2: evaluation returns
idtac
where
c := split_prefix l1 l2
of type
constr of type tacvalue

Level 2: evaluation returns
idtac
where
c := split_prefix l1 l2
of type
constr of type tacvalue

Level 2: evaluation returns
idtac
where
c := split_prefix l1 l2
of type
constr of type tacvalue