Ruby hash quirks - part 2

ruby_hash_2.rb

[1] (pry) main: 0> default_array = [];
[2] (pry) main: 0> my_hash = Hash.new default_array;
[3] (pry) main: 0> my_hash[:hobbies] << 'dancing';
[4] (pry) main: 0> my_hash[:skills]  << 'php';
[5] (pry) main: 0> my_hash[:hobbies] == my_hash[:skills]
=> true
[6] (pry) main: 0> my_hash[:hobbies] == default_array
=> true
[7] (pry) main: 0> default_array
=> ["dancing", "php"]
[8] (pry) main: 0> default_array.object_id
=> 70163812238500
[9] (pry) main: 0> my_hash[:hobbies].object_id
=> 70163812238500
[10] (pry) main: 0> my_hash[:some_random_key].object_id
=> 70163812238500