group in pairs

gistfile1.rb

#get array of cities by
#Schools.where('XX').map(&:city).uniq.sort { |a,b| a.downcase <=> b.downcase }

def group_in_pairs (arr)
  ra = []
  skip = -1
  arr.each_with_index do |a,i|
    return ra if arr[i+1].nil?
    next if skip > i
    if (a.downcase == arr[i+1].downcase)  
      ma = []
      ni = i+1
      ma.push a
      while (a.downcase == arr[ni].try(:downcase))
        ma.push arr[ni]
        ni = ni + 1
      end
      ra << ma
      skip = ni
    else
      ra << [a.titleize, a] unless a.titleize == a
    end
  end
  ra
end