I want to write Tcl but don't have the need for any programs/libraries.
Well, why don't we help you out with some suggestions, then...
1. Pure-tcl SSH client library
SSH is a very nice and rich protocol (protocol suite?) for remote communication. When using it from Tcl one usually (see e.g. remote ssh tcl, comm via ssh) runs an external cmdline client, but that doesn't allow you to reconfigure the connection once it has been set up, to e.g. add new channels for data transfer. The effect is often that homegrown multiplexing mechanisms are developed that typically are inferior to the one already built into the SSH transport layer (and thus supported natively on the server side).
From an implementation point of view, it is worth observing that the encryption and signature algorithms needed to implement SSH are already available in tcllib. That's probably more than half the work completed already!
AK - 2011-03-10 23:25:17
Python's implementation of such is called paramiko.