Pass PowerShell output to a WorkflowData parameter

Hi,

Is it possible to assign a array to WorkflowData parameter?

Also how do we assign an output from a powershell to workflowdata parameter so that this value can be used in email notification. I see that we have 3 options for the Script Return Type parameter. I used "Single Value"  and in the Return Value Look up I gave something like [//WorkflowData/PowershellOutput].

I tried using this [//WorkflowData/PowerShellOutput] in the body of the email notification template but it doesn't seem to get populated with any value when I receive the mail notification.

In the eventViewer it gives a warning message as below