Tests/RunCMake/Syntax/AtWithVariableAtOnly.cmake - third_party/github.com/Kitware/CMake - Git at Google

 set(right "wrong")
 set(var "\${right}")
 # Expanded here.
 set(ref "@var@")

 # No dereference done at all.
 string(CONFIGURE "${ref}" output @ONLY)
 message("-->${output}<--")
	set(right "wrong")
	set(var "\${right}")
	# Expanded here.
	set(ref "@var@")

	# No dereference done at all.
	string(CONFIGURE "${ref}" output @ONLY)
	message("-->${output}<--")