求教一个简略的正则表达式

求教一个简单的正则表达式
 大家好，
我有一个字符串：

<li>

                                                                <a class="thumb" href="http://farm3.static.flickr.com/2201/1502907190_7b4a2a0e34.jpg" title="Title #21">

                                                                        <img src="http://farm3.static.flickr.com/2201/1502907190_7b4a2a0e34_s.jpg" alt="Title #21">

                                                                </a>

                                                                <div class="caption">

                                                                        <div class="image-title">Title #21</div>

                                                                        <div class="image-desc">Description</div>

                                                                        <div class="download">