You should re-direct your question to http://www.perlmonks.org
for the most authoritative answer.
However, in general, the answer (for this or any other language system) is that, if you "change" the installed system in any way, you should reinstall all packages. Every language provides some means (e.g. "cpan") by which to do this.
There are several reasons why it's important:
- Packages commonly involve C-language components (in Perl, called "XS") which need to be "guaranteed compatible" with the system.
- Package installers usually make decisions based on the exact version that they detect.
- In the case of Perl, at least, exhaustive self-tests will be performed to confirm that the package continues to work properly.