if(MATCHES)
  message(SEND_ERROR "Test #1 failed")
else()
  message(STATUS "Test #1 passed")
endif()

if("" MATCHES "")
  message(STATUS "Test #2 passed")
else()
  message(SEND_ERROR "Test #2 failed")
endif()

if(MATCHES RHS)
  message(SEND_ERROR "Test #3 failed")
else()
  message(STATUS "Test #3 passed")
endif()

set(RHS "")
if(MATCHES RHS)
  message(SEND_ERROR "Test #4 failed")
else()
  message(STATUS "Test #4 passed")
endif()

if(MATCHES "^$")
  message(SEND_ERROR "Test #5 failed")
else()
  message(STATUS "Test #5 passed")
endif()

if("" MATCHES "^$")
  message(STATUS "Test #6 passed")
else()
  message(SEND_ERROR "Test #6 failed")
endif()