Add a test for double anchors, in TODO block.

t/xhtml-bkb.t

@@ -0,0 +1,24 @@
+#!/usr/bin/perl -w
+
+# t/xhtml-bkb.t - https://rt.cpan.org/Public/Bug/Display.html?id=77686
+
+use strict;
+use warnings;
+use Test::More tests => 1;
+use Pod::Simple::XHTML;
+my $c = <<EOF;
+=head1 Documentation
+
+=head2 Changes to Existing Documentation
+
+=head3 L<perldata>
+EOF
+my $d = Pod::Simple::XHTML->new ();
+$d->index (1);
+my $e;
+$d->output_string (\$e);
+$d->parse_string_document ($c);
+TODO: {
+    local $TODO = 'See bug report';
+    unlike ($e, qr!<a[^>]+><a[^>]+>!);
+};