Good suggestion on leaving LD_PRELOAD unset if it was previously unset. We will fix that.

I’m torn on whether MD_PRELOAD or LD_PRELOAF is more obnoxious to other programs.

Fun fact: A previous version of this program used an even more inscrutable `env[0][0]+=1`, which is great as a sort of multilingual C/English pun, but terrible in the way that all “clever” code is terrible.