Firefly Fluxx Upgraded Creepers
It's just "if".

The Creeper doesn't give you an extra ability to discard a Keeper. It just says what to do "if" you discard a Keeper.

Contrast this alternate wording:


  During your turn, you can discard a Keeper you have in play to move
  this to another player.


which is similar to Gold-Pressed Latinum's


  You can discard this to steal any Keeper...