Ruby hashes inconsistency

console.rb

# copy and store in another variable:
[16] pry(main)> hash1 = {a: 'asdasd', b: 'asdasd'}
=> {:a=>"asdasd", :b=>"asdasd"}
[17] pry(main)> hash2 = hash1
=> {:a=>"asdasd", :b=>"asdasd"}
[18] pry(main)> hash2.delete(:a)
=> "asdasd"
[19] pry(main)> hash2
=> {:b=>"asdasd"}
[20] pry(main)> hash1
=> {:b=>"asdasd"}
[21] pry(main)>

#shallow copy
[23] pry(main)> hash3 = {a: 'asdasd', b: 'asdasd'}
=> {:a=>"asdasd", :b=>"asdasd"}
[24] pry(main)> hash4 = hash3.clone
=> {:a=>"asdasd", :b=>"asdasd"}
[25] pry(main)> hash3.delete(:a)
=> "asdasd"
[26] pry(main)> hash3
=> {:b=>"asdasd"}
[27] pry(main)> hash4
=> {:a=>"asdasd", :b=>"asdasd"}
[28] pry(main)> hash3[:b] << ' something else'
=> "asdasd something else"
[29] pry(main)> hash3
=> {:b=>"asdasd something else"}
[30] pry(main)> hash4
=> {:a=>"asdasd", :b=>"asdasd something else"}
[31] pry(main)> 

here we see Ruby failing in multiple ways

1. delete method deletes a hash element but actually changes the hash itself. It should be delete! instead.
2. by setting the hash contents of a variable to another variable you actually have another reference to the same contents. So changing the contents of the new variable, you change the contents of the old variable too since both reference to the same address.
3. even with clone method, ruby does a shallow copy so even (2) is solved, if you change the contents of the initial variable, contents of the cloned variable will be changed. It means that although the "hash's references are being copied, but not the objects that the references refer to".
4. So you need a deep clone.