unless

gistfile1.txt

irb(main):001:0> array = ["a", "b", "c"]
=> ["a", "b", "c"]
irb(main):002:0> unless array[0] == "b"
irb(main):003:1> array << "d"
irb(main):004:1> end
=> ["a", "b", "c", "d"]
irb(main):005:0>