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

my $html = <<HTML;
<p><a id="GuidelineDataList__ctl1_doctitlelink"
href="/summary/summary.aspx?doc_id=4363">(1) Pertussis vaccination: use of
acellular pertussis vaccines among infants and young children. <br />(2) Use of
diphtheria toxoid-tetanus toxoid-acellular pertussis vaccine as a five-dose
series. (Addendum)</a>
  Centers for Disease Control and Prevention - Federal Government Agency [U.S.].
  1997 Mar 28 (revised 2000 Nov; addendum released 2003 Sep 26)
.
  25 pages.
 
  NGC:003288</p>
HTML

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

# Get a list of anchors that have an id attribute starting 'GuidelineDataList'
my @anchors = $tree->look_down (id => qr/^GuidelineDataList/);

for my $anchor (@anchors) {
  next if ! defined $anchor || ! defined $anchor->parent ();
  print 'HRef: ', $anchor->attr ('href'), "\n" if defined $anchor->attr ('href');
  print 'Text: ', $anchor->parent ()->as_text (), "\n" if defined $anchor->parent ();
}