gistfile1.builder

irb> x = [1,2,"",3, "", ""]
=> [1, 2, "", 3, "", ""]
irb> x.pop while x.last.blank?
=> nil
irb> x
=> [1, 2, "", 3]


irb> x = [1,2,"",3]
=> [1, 2, "", 3]
irb> x.pop while x.last.blank?
=> nil
irb> x
=> [1, 2, "", 3]


irb0> x = [1,2,"",3, "", ""]
=> [1, 2, "", 3, "", ""]
irb> x.pop until x.last.blank?
=> nil
irb> x
=> [1, 2, "", 3, "", ""]


irb> x = [1,2,"",3]
=> [1, 2, "", 3]
irb> x.pop until x.last.blank?
=> nil
irb> x
=> [1, 2, ""]

x = [nil,nil,nil]
x.pop when x.last.blank? #=> dead loop