There is an ongoing outage on the primary CPAN mirror. It is possible to work around the issue by using MetaCPAN as a mirror.
To install JIRA::REST::OAuth, copy and paste the appropriate command in to your terminal.
cpanm
cpanm JIRA::REST::OAuth
CPAN shell
perl -MCPAN -e shell install JIRA::REST::OAuth
For more information on module installation, please visit the detailed CPAN module installation guide.