Cork, when I tried your code I got:

* Set %test to %test2
* Set %test2 to proof-of-concept
proof-of-concept will return "proof-of-concept"
* Set %test2 to success
success will return "success"
* Unset %test2
* /unset: insufficient parameters (line 62, aliases.ini)

(I added the -s switches and tried it in Aliases without the 'alias' and Remotes with it just to be sure)

but... when I chaged the last line to:

unset % [ $+ [ test ] ]

it worked like a charm and I got:

* Set %test to %test2
* Set %test2 to proof-of-concept
proof-of-concept will return "proof-of-concept"
* Set %test2 to success
success will return "success"
* Unset %test2
* Unset %test

but I get what BlueGhost is saying, I was trying to explain where ScreeM was coming from and why BG wasn't getting the same results.