In article ,
says...

If you twist its top off with your bare hands and consume the
contents, it's probably a bear. If it does that to you, it's
most likely a bear.

HTH,
Kevin


D'oh! Let's try that again:

If you twist its top off with your bare hands and consume the
contents, it's probably a beer. If it does that to you, it's
most likely a bear.