Are built-in variables global?

[Joshua Rigler]

OK, probably a dumb question, but like the subject line asks, are 
built-in variables global in scope?

The only reason I ask is that I currently have a very long-running 
program which periodically dumps me into debug mode via the keyboard 
command.  Sometimes I am just too impatient to wait for the next 
scheduled "debug session", and I want to be able to type ctl-c to drop 
into debug mode on a whim.  The problem is that I failed to set 
debug_on_interrupt before I started the program.  I guess what I really 
want to know is whether or not I can set debug_on_interrupt at the next 
scheduled break point, and be confident that this built-in variable will 
stay set from that point forward.

FWIW, I am still running 2.1.71+forge on Fedora Core 3, self-compiled 
and linked to multithreadded ATLAS BLAS libraries...not exactly "off the 
shelf".

Thanks.

-EJR