Assuming each letter is in an H2 tag (and that these are the only H2 tags) and that each structure is identical.

This should do the trick. We collect the data into a HoH (%href).

Hope this helps.

my $p = HTML::TokeParser::Simple->new(\$html);
my (%href, $this_href, $number, $letter);

while (my $t = $p->get_token){
  
  if ($t->is_start_tag('h2')){
    $letter = $p->get_trimmed_text('/h2');
    next;
  }
  
  if ($t->is_start_tag('a')){
    # skip bookmarks
    next if $t->get_attr('name');
    $this_href =  $t->get_attr('href');
    next;
  }
  
  if ($t->is_start_tag('span')){
    $number = $p->get_trimmed_text('/span');
    $href{$letter}{$this_href} = $number;
    next;
  }
  
}
[download]

output

---------- Capture Output ----------
> "C:\Perl\bin\perl.exe" _new.pl
A
    pdf\8a956f66-1c60-48fc-905c-b49d617aa6c5.pdf -> 110377660
    pdf\c76b834e-36e1-497b-b13e-eba2348dc044.pdf -> 110136892
    pdf\ae8d51e0-005b-44be-84cb-3c9b57335755.pdf -> 108318866
    pdf\37d3e78b-1adb-458b-9e89-0df780909f08.pdf -> 108116112
    pdf\e646f948-f78d-4463-a01d-0261aebf70dc.pdf -> 113069066
    pdf\6c0a5bb4-143d-4305-957b-796c8193d07a.pdf -> 116815754
B
    pdf\8a956f66-1c60-48fc-905c-b49d617aa6c5.pdf -> 110377660
    pdf\c76b834e-36e1-497b-b13e-eba2348dc044.pdf -> 110136892
    pdf\ae8d51e0-005b-44be-84cb-3c9b57335755.pdf -> 108318866
    pdf\37d3e78b-1adb-458b-9e89-0df780909f08.pdf -> 108116112
    pdf\e646f948-f78d-4463-a01d-0261aebf70dc.pdf -> 113069066
    pdf\6c0a5bb4-143d-4305-957b-796c8193d07a.pdf -> 116815754
C
    pdf\8a956f66-1c60-48fc-905c-b49d617aa6c5.pdf -> 110377660
    pdf\c76b834e-36e1-497b-b13e-eba2348dc044.pdf -> 110136892
    pdf\ae8d51e0-005b-44be-84cb-3c9b57335755.pdf -> 108318866
    pdf\37d3e78b-1adb-458b-9e89-0df780909f08.pdf -> 108116112
    pdf\e646f948-f78d-4463-a01d-0261aebf70dc.pdf -> 113069066
    pdf\6c0a5bb4-143d-4305-957b-796c8193d07a.pdf -> 116815754

> Terminated with exit code 0..
[download]