It sounds like you don't need to use both version 7 and 8 from the same script, which makes things easier (if you did, that'd make things pretty complicated). You could install the modules to different, custom library paths. Hopefully, the modules use one of the standard Perl installation procedures: If it's ExtUtils::MakeMaker, run perl Makefile.PL INSTALL_BASE=/path/for/v7 resp. /path/for/v8 (the paths where you want to have the libraries installed); if it's Module::Build, run perl Build.PL --install_base /path/for/v7 resp. v8. Then, in your Perl scripts, you can point them at the correct library path, for example with use lib '/path/for/v7/lib/perl5' before loading the module.