irb(main):001:0> d = [1,2,3,4]
=> [1, 2, 3, 4]
irb(main):002:0> h = Hash.new
=> {}
irb(main):003:0> h[d] = "hello"
=> "hello"
irb(main):004:0> h
=> {[1, 2, 3, 4]=>"hello"}
irb(main):005:0> h[d]
=> "hello"
irb(main):006:0> d.push(5)
=> [1, 2, 3, 4, 5]
irb(main):007:0> h[d]
=> nil
irb(main):008:0> h
=> {[1, 2, 3, 4, 5]=>"hello"}
irb(main):009:0> d
=> [1, 2, 3, 4, 5]
irb(main):010:0> h[d]
=> nil
irb(main):011:0> h.rehash
=> {[1, 2, 3, 4, 5]=>"hello"}
irb(main):012:0> h[d]
=> "hello"
irb(main):013:0>


Is this expected or a bug?

-abhisek