function login__from_env()

function user2path($user) # multiple @ and nested . OK: a@b.c@url -> url?b.c.a

{

	$path = $user;

	# remove padding used to visually separate elements: x__@y__@url -> x@y@url

	# this leaves embedded __ (eg. x__y) untouched

	$path = preg_replace('/\b__|__\b/', '', $path);

	# remove insertion comments: [c]x[d]@url -> x@url

	# use [] because in writing, [] denotes insertion

	# insertion indicates that the semantic meaning of the [] portion also

	$path = preg_replace('/\[.*?\]/', '', $path);

	# remove deletion comments: (-c_-)x@url -> c_x@url

	# use () because in editing, () denotes something to remove

	# the -...- indicate strikethrough (deletion)

	# deletion indicates that the semantic meaning of the () portion does not

	$path = preg_replace('/\(-([^)]*?)-\)/', '$1', $path);

	# translate reverse @-paths into forward .-paths

	$path = implode(".", array_reverse(explode("@", $path)));

	# undo transposes: _y~x@url -> x_y@url , Y~x@url -> xY@url

	# these can be used to put the category in a column name first

	# the _ should go first so that _y~ lines up vertically with [y_] paths

	# can't use : for this because Firefox will not update the "password" for

	$path = preg_replace('/([^.]*)~([^.]*)/', '$2$1', $path);

	return $path;

}

	header('WWW-Authenticate: Basic realm="'

}

	$dest = preg_replace('!\b/!', "./", $_SERVER["SCRIPT_URI"])."?";

	if ($_SERVER["PHP_AUTH_USER"] !== "") # prepend to query string

		$dest .= "."/*force dotpath*/.user2path(login__from_env());

	$dest .= $_SERVER["QUERY_STRING"];

}