# In Ruby 2.5, append and prepend are implemented as aliases to the original unshift and push methods.
a = ["hello"]
# => ["hello"]
a.append "world"
# => ["hello", "world"]
a.prepend "Hey"
# => ["Hey", "hello", "world"]
array = [1, 2, 3, 4]
array.push(5)
array # => [1, 2, 3, 4, 5]