$def with (return_url)
$var title: Sign In

<h3>For Guests</h3>
<form action=/guests/sign-in>
<div><label>Your website<br>
<input type=hidden name=return_url value="$return_url">
<input type=text name=me placeholder="https://me"></label></div>
<button>Sign In</button>
</form>

<h3>For Site Owner</h3>
<form action=/owner/sign-in method=post>
<div><label>Passphrase<br>
<input type=hidden name=return_url value="$return_url">
<input type=text name=passphrase></label></div>
<button>Sign In</button>
</form>