From: Paul Brannan <pbrannan@...>
Date: 2008-09-06T01:03:04+09:00
Subject: [ruby-core:18461] Re: Global constants and other magic in 1.9	stdlib

On Fri, Sep 05, 2008 at 01:44:23AM +0900, Daniel Luz wrote:
> I should note that $?, along with $_ and many regexp-related
> variables, is actually thread-local, despite its apparently-global
> name.

$_ is thread-local, but $? really is global:

  rb_define_readonly_variable("$?", &rb_last_status);

I'm sure there's a good reason, but I don't know what it is. (maybe
something to do with calling Process.wait from a signal handler?)

Paul