Problems with Perl 5's switch

I was trying to use perl's __DATA__ subsection and was receiving the following warnings/errors:

readline() on unopened filehandle DATA
main::DATA used only once

Well, after fighting with it for like 20 minutes, I did a Google search. After wandering around different mailing list archives, etc, I finally found a hint of a solution.

Apparently, using "Switch" (via "use Switch;") does some kind of behind-the-scenes magic that breaks __DATA__ section stuff.

I didn't find anything in perldoc Switch that indicated it was a known bug. However, it is v5.8.5 so fairly old (2004, from RHEL 4.5) and the Switch documentation says it is from 2003.

Annoying tho.