I use a WinNT machine with two versions of ActiveState Perl installed in two different directory trees next to each other.

I usually use an environment variable set to the location of the "right" one of the two perl interpreters (perl.exe) to switch between the two versions. I have not set up any file type associations, but use ".bat" files to call the perl scripts (pl2bat is your friend).

This has worked well for me until now.

Christian Lemburg
Brainbench MVP for Perl
http://www.brainbench.com