CSS Feature Detection: CSS3 Shadow

CSS Feature Detection: CSS3 Shadow

(can be integrated inside jquery core function 'jQuery.support')

I'm working on a shadow feature detection.
The idea is simple: if the browser have CSS3 shadow support, we will use it. Otherwise we will create a shadow box manually.

It's working very well so far! But I can't detect this on Opera.
Any ideas how to fix this? Any suggestion to improve this code?

/**
 * CSS Feature Detection: Shadow
 * Tested on: Firefox 3.0.18 and 3.6, IE 6, 7, 8, Chrome 5, Opera 10.5, Safari 4.0.5
 * On Opera we can't detect correctly. (todo)
 *
 * Author: Tiago Fischer (tiagofischer@gmail.com)
 */
function featureDetectionShadow() {
    var flagDetection = false;
    function shadowDetection($handle, css) {
        try {
            var shadow = $handle.css(css);
            if (shadow != 'null' && shadow != '') {
                var regTest = String(shadow.match(/AAAAAA/i));
                if (regTest != '') {
                    flagDetection = true;
                }
            }
        } catch(err) { };
    }           
    var $testOne = $('<div></div>').css('-moz-box-shadow', '0px 0px 8px 5px #AAAAAA');
    var $testTwo = $('<div></div>').css('-webkit-box-shadow', '0px 0px 15px #AAAAAA');
    var $testTree = $('<div></div>').css('box-shadow', '0px 0px 8px 5px #AAAAAA');
    shadowDetection($testOne, '-moz-box-shadow');
    shadowDetection($testTwo, '-webkit-box-shadow');
    shadowDetection($testTree, 'box-shadow');           
    return flagDetection;   
}