I recently installed THE 3.3beta3 along with Regina 3.4 on Linux and it works great.
Just for a lark I tried to install THE with ooRexx. I had trouble installing it and had to modify the Makefile but finally got it installed.
Only to find out that ooRexx runs much much slower than Regina.
So I uninstalled ooRexx and tried to forget the experience...
If I were to pick another "OO" language to run under THE, I might pick Python.
Given similar programs to run, Python 2.5.1 runs faster than Regina 3.4
The "decimal" module written for Python is based on standards written by Mike Cowlishaw
and allows Python to do the same kinds of arithmetic as Rexx.
I don't know if the oo language Ruby has this "decimal" feature or not.
Can you quantify 'much slower than Regina'? I have an old Gateway with a rexxcps=1216057 and I find the performance of ooRexx acceptable, given everything that's going on under the covers to make everything an object.