in reply to changing vaules in perl -V
That value is set when perl is Configured as part of its installation process. You'll have to rebuild Perl to change it.
You can override most if not every path when you install a module. But in this case, the solution is much simpler:
ormv /usr/local/bin/cpanm /usr/bin/
ln -s /usr/local/bin/cpanm /usr/bin/
In Section
Seekers of Perl Wisdom