The field of problems that are a) always errors, b) detectable, and c) easily made unintentionally is not very large. Also, the docs for 'strict' specifically mention 'vars' as being intended to prevent variable suicide - which it fails to do in this case. Currently, the only thing that we've got is a mildly-phrased warning; in fact, it's classified as 'misc' in the warnings hierarchy.
That just seems totally inappropriate to me - particularly when compared to the way this kind of error is treated in other languages.
I hate storms, but calms undermine my spirits.
-- Bernard Moitessier, "The Long Way"