p.rb

require 'rubygems'

module Kernel
  alias :default_p :p

  def p(*args, &block)
    case RUBY_PLATFORM
    when /linux/
      require 'n'
      n(*args, &block)
    when /darwin/
      require 'g'
      g(*args, &block)
    end
  rescue
    default_p(*args, &block)
  end
end