The
is
operator does not match the values of the variables, but the instances themselves.
What does it really mean?
Prompted by a duplicate question, this analogy might work:
# - Darling, I want some pudding!
# - There is some in the fridge.
pudding_to_eat = fridge_pudding
pudding_to_eat is fridge_pudding
# => True
# - Honey, what's with all the dirty dishes?
# - I wanted to eat pudding so I made some. Sorry about the mess, Darling.
# - But there was already some in the fridge.
pudding_to_eat = make_pudding(ingredients)
pudding_to_eat is fridge_pudding
# => False