Goal:
  
  A : Type
  a : A
  l : list A
  i : nat
  a0 : A
  IHl : skipn i l = a0 :: skipn (S i) l
  ============================
   (a0 :: skipn (S i) l = a0 :: skipn (S i) l)


DEBUG:Going to execute:
fun => <coq-core.plugins.ltac::reflexivity@0>