while the second [...] allows anything NOT /BARZ/ followed by (your dot_deathstar, .* any number of any characters INCLUDING /BARZ/

That's why I had added but of course this is not quite right, since it would also reject FOOBARX, but you are right that I should have been much more clear in my OP. I had included the (wrong) approach so that you don't believe I would just ask for help without at least trying to solve it on my own, but in the way I did it, it just caused a lot of confusion....