title: Whether to escape ( and ) in regex using GNU sed
body: <p>I've noticed several posts on this site which say that with gnu sed you should use <code>(</code> and <code>)</code> in regex rather than <code>\(</code> and <code>\)</code>.  But then I looked in the <a href="http://www.gnu.org/software/sed/manual/sed.html#The-_0022s_0022-Command" rel="noreferrer">gnu sed manual</a> and saw that they specify that <code>\(</code> and <code>\)</code> must be used.  What's up?</p>