array flatten with level for ruby 1.8.7

straight to the code:

class Array
  alias_method :orig_flatten, :flatten
  
  def flatten level=nil
    if level.is_a?(Integer)
      temp_arr = clone
      level.times{ |i| temp_arr = temp_arr.inject([]){|s,v| v.is_a?(Array) ? s.concat(v) : s << v} }
      temp_arr
    else
      orig_flatten
    end
  end
end

of course although untested i'm sure it will have worse performance than the original flatten in ruby 1.9.2, but better than nothing right? ;)