Could you try to reduce the code to the minimum needed to reproduce the problem? (http://sscce.org/)

I've seen people suggest its use once in a while so I don't want to spread too much FUD, however, it might be noteworthy that Net::OpenSSH::Parallel was last released over two years ago and has no test suite. Quote from Net::OpenSSH::Parallel: "Some people find easier to use Net::OpenSSH combined with Parallel::ForkManager, ..."