ress this error via <code>--undefok=foo</code>, just like
for any other flag.)</p>

<p>It is also a fatal error to say <code>--fromenv=foo</code> if
<code>FLAGS_foo</code> is not actually defined in the environment.</p>

<h3> <code>--tryfromenv</code> </h3>

<p><code>--tryfromenv</code> is exactly like <code>--fromenv</code>,
except it is <b>not</b> a fatal error to say
<code>--tryfromenv=foo</code> if <code>FLAGS_foo</code> is not
actually defined in the environment.  Instead, in such cases,
<code>FLAGS_fo