El Capitan SIP and CPAN
You can install a newer version of cpan in /usr/local/bin with the following CPAN configuration:

cpan
cpan&gt; o conf makepl_arg "INSTALLBIN=/usr/local/bin INSTALLSCRIPT=/usr/local/bin"
cpan&gt; o conf commit
cpan&gt; exit
sudo cpan -i CPAN


This solution, and others, is discussed at perlmonks.