Rubyの%記法

[1] pry(main)> %w(a i u)
=> ["a", "i", "u"]
[2] pry(main)> %i(a i u)
=> [:a, :i, :u]

http://simpleror.wordpress.com/2009/03/15/q-q-w-w-x-r-s/
http://docs.ruby-lang.org/ja/1.9.3/doc/spec=2fliteral.html#percent