content: sub main()
    myVar = invalid
    RightInvalid(myVar)
    LeftInvalid(myVar)
  end sub
  
  sub RightInvalid(param1 as object)
    if param1 <> invalid
       param1.id = 1
    else
       print "param invalid"
    end if
  end sub
  
  sub LeftInvalid(param1 as object)
    if invalid <> param1
       param1.id = 1
    else
       print "param invalid"
    end if
  end sub