I used this command to install Nagios::Plugins on multiple servers months/weeks before:
perl -MCPAN -e 'install Nagios::Plugin'
Now I get this error message:
Reading '/root/.cpan/Metadata' Database was generated on Mon, 27 Apr 2015 00:29:02 GMT Warning: Cannot install Nagios::Plugin, don't know what it is.
As far as I can tell, the module is still in CPAN: http://search.cpan.org/dist/Nagios-Plugin/