[Radiant] How to use 0.8.1 and 0.9 on the same machine?

[Horst Rischbode]

Hello,

on my development machine, I'm on 0.8.1. Now I want to switch to 0.9. 
But I still need to be able, to support the old version.

How to install 0.9 together with 0.8.1?

Any help would be appreciated!

Horst