I could not tell from the docs if Net::SSH2 is thread-safe or not. It would be nice to have this kind of info in the META.yml file ;)

Now regarding Net::SSH::Perl I would not consider it antiquated, and it has its use: you can look at it almost as a pure-perl implementation (modulo a maths lib that someday could be part of core perl). It is true that the maintainer himself says that the module is showing signs of age and is hard to maintain but mostly IMHO because implementations of SSH1 and SSH2 are shipped in the same module (and even use different libs!).

Another aspect is that building libssh2 is not so easy, and till recently there was no package on cygwin for it. Checking now I can see one libssh2; will try later to build Net::SSH2.

I am quite fond of pssh actually; it is easy to hack: for example if you want to do local env management and run a few remote commands automatically before opening up a remote interactive shell.