f
<code>*Allow</code> is non-<code>NIL</code>, <code>sym</code> is added to the
<code><a href="refI.html#idx">idx</a></code> tree in the CAR of
<code>*Allow</code> (if <code>flg</code> is <code>NIL</code>), or to the list of
prefix strings (if <code>flg</code> is non-<code>NIL</code>). See also <code><a
href="refA.html#allowed">allowed</a></code>.

<pre>
: *Allow
-> (("!start" ("!psh") "!stop" NIL "lib.css") "app/")
: (allow "!myFoo")  # additionally allowed item
-> "!myFoo"
: (allow "myDir/" T)  # addition