like this

#!/usr/bin/perl --

use strict;
use warnings;
use HTML::TreeBuilder;

my $html = <<'__HTML__';
<a href="http://www.yahoo.com" target=_blank><img
src="http://us.i1.yimg.com/nw.gif" 
alt="Open this result in new window"></a>
<a href="http://www.yahoo.com" target=_blank><img
src="http://us.i1.yimg.com/nw.gif" 
alt="Two clues"><img
src="http://us.i1.yimg.com/nw.gif" 
alt="for the price of one"></a>
__HTML__


{
  my $h = HTML::TreeBuilder->new_from_content($html);

  for my $link ( $h->look_down( _tag => q{a}, href => 'http://www.yaho
+o.com' ) )
  {
    print $link->attr('href'),"\n";
    my $text = $link->as_trimmed_text;
    unless ($text) {
      $text = join ' ',
        map { $_->attr('alt') } $link->look_down( alt => qr/^.+$/ );
    }
    print "$text\n\n";
  } ## end for my $link ( $h->look_down...)

}

__END__
http://www.yahoo.com
Open this result in new window

http://www.yahoo.com
Two clues for the price of one
[download]