Flatten a hash's structure in a somewhat naive way

mash.rb

#!/usr/bin/env ruby

class Hash
  def mash(prefix=nil)
    reduce({}) do |a, (k,v)|
      case v
      when Hash then a.merge(v.mash(k.to_s + '_'))
      else a.merge({ "#{prefix}#{k}" => v })
      end
    end
  end
end

h = { 'a' => { 'b' => 1, 'c' => 2 } }
pp h.mash  # {"a_b"=>1, "a_c"=>2}