VAR = qt thread
VAR += debug
!contains( VAR, debug ) {message("FAILED: +=")}
VAR -= thread
contains( VAR, thread ) {message("FAILED: -=")}
VAR = thread
VAR *= thread
!count( VAR,1) {message("FAILED: *=")}
VAR = thread QT_DLL debug
VAR ~= s/QT_+/Q_
!contains( VAR, Q_DLL ) {message("FAILED: ~=")}