CPAN Testers for PAR::Packer 1.025 shows hundreds of passed tests on 64-bit platforms, and there is no general problem with Perl on 64-bit systems. Could you provide some more information please? What versions of Perl? Did you build them yourself or are they the system Perl? How are you trying to install the modules (package manager, cpan, built yourself, ...)? What error messages are you getting? If you think it's an issue with a script and not a module, could you provide a short example script that reproduces the problem (works on 32-bit but not on 64-bit)?