Odd but valid syntax for retrieving keys or values from an object

gistfile1.as

// Originally by @pleclech
//  via http://pastebin.com/1MDyFVJA

var o:Object = { foo:"bar", hello:"world", one:"one", two:"two" };

var values:Array = [];
for each (values[values.length] in o);
trace(values); // world,one,two,bar

var keys:Array = [];
for (keys[keys.length] in o);
trace(keys); // hello,one,two,foo