Generally, you report issues with CPAN modules to the maintainer listed in the module's CPAN page or README file.

Also, a module's page on MetaCPAN has links to the module's test matrix on http://cpantesters.org, which has a link to a dependences report near the bottom.

Looking at http://matrix.cpantesters.org/?dist=Net-SSH-Perl+1.42, Net::SSH::Perl passes on Perl 5.20.1 and 5.20.2

As for Math::Pari, the documentation for it indicates that libPari needs to be installed before trying to install Math::Pari