michael@0: 'abcdef'.replace(/a(\w+)c/, function() {
michael@0:     assertEq(RegExp.lastMatch, 'abc');
michael@0:     '123456'.replace(/1(\d+)3/, function() {
michael@0:         assertEq(RegExp.lastMatch, '123');
michael@0:     });
michael@0:     assertEq(RegExp.lastMatch, '123');
michael@0: });
michael@0: assertEq(RegExp.lastMatch, 'abc');
michael@0: