问题
I downloaded the 5.12.3 installer to upgrade my 5.12.1 installation. After installing 5.12.3, my previously installed cpan modules are gone. Is this expected behavior? Should I be backing up my library before upgrading to prevent this?
回答1:
It is expected behavior. Next time you can use "autobundle" feature of CPAN client, it will create list/bundle of modules to reinstall using CPAN client in new version.
回答2:
I would claim that this should not be expected behavior.
The site directories are not part of the standard distribution and should not be touched by the distribution. Heck, it's even why the site directories even exist. Otherwise, why not simply download all of the modules to the same directory? Why make a distinction between the standard Perl modules and the modules you download from CPAN?
I too found this out the hard way when my personal modules -- modules that are not part of CPAN -- were blown away by my upgrade of Strawberry Perl. ActivePerl does it right -- not only not touching the site directory, but also adds in the Perl version to the standard module directory and the site directory.
来源：https://stackoverflow.com/questions/6101682/how-do-i-upgrade-strawberry-perl-without-wiping-perl-site-lib-and-perl-site-b