They're both zero width matchers so having multiple of them should work.  It works in all the browsers from our test suite.  I've added a test for it.  https://github.com/chirayuk/angular.js/commit/f93ca0ec55e2901e1a31617c9217ef68b55bf44a#diff-a8764a108e44aa116347d682fbce8b18R301