I'm not sure I'm getting your requirement here. Are you trying to:

      home host --- ssh connection ---> intermidiate host -- ssh --> h
+osta
                                                                     h
+ostb
                                                                     h
+ostc
[download]

If it is, why not cut out the middle man?

As far as using a module to connect where a password is required I am positive there are CPAN modules that do that since I've written quite a few scrips over the years that use that behavior.

Wait until CPAN comes back and check out http://search.cpan.org using "ssh" as a search term.