class Array

def split(value = nil, &block)

(1..10).to_a.split { |i| i % 3 == 0 } # => [[1, 2], [4, 5], [7, 8], [10]]
[1, 2, 3, 4, 5].split(3) # => [[1, 2], [4, 5]]

or the result of an optional block.
Divides the array into one or more subarrays based on a delimiting +value+ 
def split(value = nil, &block)
  arr = dup
  result = []
  if block_given?
    while (idx = arr.index(&block))
      result << arr.shift(idx)
      arr.shift
    end
  else
    while (idx = arr.index(value))
      result << arr.shift(idx)
      arr.shift
    end
  end
  result << arr
end