Not a direct answer... but do you really need to use Net::SSH::Perl? Have you already considered using Net::SSH2 instead?  The latter module is based on the actively maintained library libssh2, while Net::SSH::Perl has already gathered some dust, has a number of unresolved bugs, and is generally dreadfully slow.  In other words, if Net::SSH2 is an option, your problem with Math::Pari might already be "solved" indirectly...