I worked with expect (tcl based automation tool) for a while back in the 90's and while I really liked expect for what it could accomplish, tcl itself annoyed me. I can't really articulate why (perhaps just the overwhelming prevalence of {} characters?) I also found pass by name semantics sort of weird, but on the other hand, I was much less mature then than I am now, so I can't really trust my own impressions.

Expect is still pretty neat:

http://expect.sourceforge.net/