The Net::SSH::Perl error about Math::Pari is quite common. It means you don't have the pre-requisite math libraries installed, and that was the reason Net::SSH2 was developed, to avoid all the dependencies.

For Net::SSH2, all you should really need is Openssh. Correction: Not Openssh but libSSH2 . Thanks, salva 

When you have trouble installing modules, it helps to download the module's source tarball, then read the included files, where they discuss the dependencies issues.