How do I find the key of a specific hash element?

For example:

my %weekdays = (
	0  => "SUN",
	1 => "MON",
	2 => "TUE",
	3 => "WED",
	4 => "THU",
	5 => "FRI",
	6 => "SAT",
);
$weekdays{2}; # gives "TUE"

But what if I know "TUE" and want to find out what the key is? Is
there a construct like $weekdays{"TUE"} that gives 2"