gistfile1.rb

class Animal
  def initialize(name)
    @name = name
  end

  def to_s
    @name
  end
end

result = [Animal.new("Pera"), Animal.new("Djura")].to_s

# in ruby 1.9
puts result # => "[Pera, Djura]"

# in ruby 2.0
puts result # => "[#<Animal:0x00000002266b08 @name=\"Pera\">, #<Animal:0x00000002266ab8 @name=\"Djura\">]"

# in other words
#   - in ruby 1.9 an array calls recursively `to_s` on its elements
#   - in ruby 2.0 an array calls recursively `inspect` on its elements