gistfile1.txt

irb(main):001:0> thing
NameError: undefined local variable or method `thing' for main:Object
	from (irb):1
irb(main):002:0> defined? thing
=> nil
irb(main):003:0> thing = thing
=> nil
irb(main):004:0> thing
=> nil
irb(main):005:0> defined? thing
=> "local-variable"

>> thing2 = raise "z"
RuntimeError: z
	from (irb):1
>> thing2
=> nil