I've accepted now that my "generalized break" was a bad idea. In
an eval context, I'll probably just define a "quit" method that
will throw :quit and that will be fine.

I'm thinking (again) about the idiom "if $0 == __FILE__" and
trying to come up with viable alternatives.

It seems to me that we don't really need an "executable" thing
like exit/break/return/quit in this context.

It could just be a "marker" as someone suggested.

My two favorites so far are __TEST__ and __MAIN__.

As far as I can see, there should be no conflict or interaction
with the __END__ marker.

Comments?

Hal