I tried your code and I got the following error....
Can't call method "right" without a package or object reference at C:\Change\2539\testit2.pl line 21.
I modified the code to look like this:
use strict;
use warnings;
use HTML::TreeBuilder;
my $root = HTML::TreeBuilder->new ();
$root->parse_file ("c:\\change\\2539\\index.html");
for ($root->look_down ('_tag', 'a')) {
my $href = $_->attr ('href');
next if ! $href;
my $sib = $_->right ()->right ();
my $number = $sib->as_text ();
print "$href: $number\n";
}