in reply to
Change package name on the fly?
You could build and install the same version of Perl on your system twice. Just when you run Configure to build and install your second version use --prefix=/some/where/else. Then install the module you want to test in both Perl's. Something like
$ /where/you/put/bin/perl -MCPAN shell
cpan> install NWCLARK/Foo-Bar-0.02.tar.gz
$ /some/where/else/bin/perl -MCPAN shell
cpan> install NWCLARK/Foo-Bar-0.01.tar.gz
Then in your test script just change the shebang.