From:	Ted Zlatanov	Date:	Thu Aug  7 10:01:56 2008
Subject:	Re: Devel::Callsite is a better instance key than join $;,caller()[1,2]

I plan to add the interpreter (Perl context, actually) address when I
get a chance, Ben Morrow was kind enough to point out what I was
missing.  Then it will be more correct than the current version.  Does
anyone know if the context address is unique in mod_perl and with
threads?  If not, what can I do?

Ted