Never mind, I got it ("Var=Value" or "Var=").
But I'm having a problem. I use Command(L"SETLOCAL", 0) and Command(L"ENDLOCAL", 0) in a plugin command and environment variables that I set in between are still there later. Doesn't SETLOCAL work in this situation?
P.S., Is SetEVariable interchangeable with SetEnvironmentVariable?