There is an ongoing outage on the primary CPAN mirror. It is possible to work around the issue by using MetaCPAN as a mirror.
No POD found for Singletons.pm. Time to read the source?
Singletons.pm
To install PPI, copy and paste the appropriate command in to your terminal.
cpanm
cpanm PPI
CPAN shell
perl -MCPAN -e shell install PPI
For more information on module installation, please visit the detailed CPAN module installation guide.