The CPAN shell has a useful command called r , which presents you with a list of modules that are apparently not up to date. Reinstalling Modules That Are Out of Date To reinstall modules that are out of date, you need to do a little programming. To quiet things down you'll need to change this. When a module depends on one or more other modules, CPAN.pm tracks those dependencies and tries to install updated versions of those modules beforehand, recursing through multiple levels of dependencies if necessary. If you are writing programs to automatically reinstall updated versions of modules, you should probably have CPAN automatically reinstall any modules that they depend on.
Some modules are a bit resistant to automatic installation.
If you run some kind of auto-update as a cron job, you will want to consider the consequences of failed installs, as well as what happens when you successfully install a module that is either buggy or no longer compatible with your current Perl programs. Sooner or later it will happen. But if you want to just keep up with the latest and greatest on your own machine, or set up a machine specifically for the purpose of debugging software against the latest and greatest Perl modules, then you will certainly want to consider using CPAN.pm to automate the updating process. In general, you can't just copy a Perl installation from one machine to another. You have to reinstall Perl and then reinstall all the modules that were present in the original installation.