accessing a process variable from a powershell script

Hi everybody,

I'm new to bonita and while playing around I get stuck when I try to use a process variable inside a (otherwise unmeaningful) powershell script called from script-connector.
Pressing ctrl+space inside the script pane shows the process variables defined. Clicking on the desired one makes it appear as ${myProcessVariable}.
Unfortunately it never gets used in the script, neither with curly brackets nor without...

ps-code goes like this: