Working with the hex representation of the bytes adds complexity, so I started by converting the hex to bytes.

You didn't specify the type of TAG and LENGTH. I appear to have guessed wrong, or your data is broken.

use strict;
use warnings;

my $fh;
{
   my $data = do { local $/; <DATA> };
   $data =~ s/\s//g;
   $data = pack('H*', $data);
   open($fh, '<', \$data) or die;
}


my $rv = read($fh, my $hdr, 13);
die "$!\n" if !defined($rv);
die "Premature EOF\n" if $rv != 13;

for (;;) {
   $rv = read($fh, my $blk_hdr, 2);
   die "$!\n" if !defined($rv);
   last if !$rv;
   die "Premature EOF\n" if $rv != 2;

   my ($tag, $len) = unpack('CC', $blk_hdr);
   --$len;
   printf("tag:  0x%02x\n", $tag);
   print("len:  $len\n");

   $rv = read($fh, my $blk_data, $len);
   die "$!\n" if !defined($rv);
   die "Premature EOF\n" if $rv != $len;

   print("data: ", unpack('H*', $blk_data), "\n\n");
}

__DATA__
84 47 00 0c 00 00 11 0a 03 50 35 04 00 64 0a 04
16 12 00 1e 00 1d 00 00 65 09 08 54 52 03 2f 82
05 10 00 02 6e 06 0b a8 53 11 67 00 00 00 7a 7f
00 69 4a 42 47 48 4a 41 0c 00 6a 53 54 4d 44 54
4f 1c 00 66 04 00 00 84 43 00 0c 00 00 11 09 08
43 49 29 60 64 0a 04 16 12 00 21 00 1b 00 00 65
09 08 44 80 90 0f 82 05 10 00 04 6e 06 08 ac 9b
02 67 00 00 00 7a 7f 00 69 53 54 4d 44 54 49 1f
00 6a 4b 43 47 48 51 42 3d 00
[download]

tag:  0x64
len:  9
data: 041612001e001d0000

tag:  0x65
len:  8
data: 085452032f820510

tag:  0x00
len:  1
data: 6e

tag:  0x06
len:  10
data: a85311670000007a7f00

tag:  0x69
len:  73
data: 4247484a410c006a53544d44544f1c00660400008443000c0000110908434929
+60640a0416120021001b00006509084480900f82051000046e0608ac9b02670000007
+a7f006953544d

tag:  0x44
len:  83
Premature EOF
[download]