I dunno, this didnt seem to be too dificult, so I have a feeling ive gone wrong here somewhere. But heres my go.

use strict;
use warnings;

foreach ('<td><img src="foo.jpg">'.
         '<a href="index3.html">New index</a></td>',
         '<td><a href="index3.html">New index</a></td>') {
         if (/<td>(?:<img[ ]src="([^"]+)">)?
              <a[ ]href="([^"]+)">((?:(?!<\/a>).)*)
              <\/a>/six) {
             print "Matched!\tImg=",
                   ($1 ? $1 : 'None'),
                   "\tLink: $2\t Link Text: $3\n";
         }
}
[download]

sorry about the weird look of the code its mostly like that to fit average settings on the site.