# 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 = []
array << "element 1"
array.append "element 2"
puts array
# ["element 1", "element 2"]