As an aside, I tried to relocate the following but cannot seem to at the moment: I believe that either Randal Schwartz or Brian D Foy did a Perlcast this summer that had a fairly good description (and possibly a Q&A) of maintaining separate Perl versions. I'll try to look again later.
"The trouble with having an open mind, of course, is that people will insist on coming along and trying to put things in it." - Terry Pratchett