Array#squeeze! require 'facets/array/squeeze' Destructive version of Enumerable#squeeze. a = [1,2,2,3,3,2,1] a.squeeze! a.assert == [1,2,3,2,1] a = [1,2,2,3,3,2,1] a.squeeze!(3) a.assert == [1,2,2,3,2,1]