PL/TCL Unkown module

Can anyone ta;lk to me about the PL/TCL implementation of the Unkown
function?

The docs are nice, but more of a tease.
http://www.postgresql.org/docs/8.3/static/pltcl-unknown.html

I have to make this work on Windows and Linux. I'm the Windows guy, I'll
have to explain this to the Linux guy!

I have the folder contents of postgresql-8.3.10\src\pl\tcl from a Linux
build. From what I see it looks like I need to run the pltcl_loadmod.in as
tcl script after every server start or bounce - could that be right?