module Enumerable

def including(*elements)

# => ["David", "Rafael", "Aaron", "Todd"]
["David", "Rafael"].including %w[ Aaron Todd ]

# => [ 1, 2, 3, 4, 5 ]
[ 1, 2, 3 ].including(4, 5)

Returns a new array that includes the passed elements.
def including(*elements)
  to_a.including(*elements)
end