Thanks for the replies.I should have specified that my question concerned my GSoC project for adding language bindings to scripting languages, with the initial focus on allowing access to the GUI elements of the Haiku API.
For that purpose, I don't think shell scripting or emacs are relevant. And since Tcl seems to be rather tightly bound to Tk as its GUI, I don't think it is a good target. That's why I left PHP off my initial list, even though I assume it works on Haiku; for the most part, I don't think PHP users are interested in writing GUI programs in PHP.
But I welcome counter-arguments to any of the points in the paragraph above. So now I have the following list: Lua Perl Python Ruby Scheme Squirrel