p { background: lime; }
[title~="hello world"] { background: red; }
/* Section 6.3.1: Represents the att attribute whose value is a
space-separated list of words, one of which is exactly "val". If this
selector is used, the words in the value must not contain spaces
(since they are separated by spaces). */

  <p title="hello world">This line should have a green background.</p>