There is an ongoing outage on the primary CPAN mirror. It is possible to work around the issue by using MetaCPAN as a mirror.
Module Install Instructions
To install , copy and paste the appropriate command in to your terminal.
cpanm NANIS/Template-Plugin-CommonMark-1.000_001.tar.gz
perl -MCPAN -e shell
install NANIS/Template-Plugin-CommonMark-1.000_001.tar.gz
For more information on module installation, please visit the detailed CPAN module installation guide.