Combining all the responses:

#!perl

use strict;
use warnings;
use Socket;
use MIME::Base64; # in core, thanks choroba

my $blob = "BAABAAXwAACGAAAAAAABLAAAAAAAAAAArBQEKA==";

$blob = decode_base64($blob);

my (
    $dataLength,    # 2 bytes
    $type,          # 2 bytes
    $version,       # 1 byte
    $rank,          # 1 byte
    $flags,         # 2 bytes 
    $serial,        # 4 bytes 
    $ttl,           # 4 bytes 
    $reserved,      # 4 bytes 
    $timestamp,     # 4 bytes
    $data ) = unpack( 'S S C C S L N L L a*', $blob );
# http://www.perlmonks.org/?node_id=1152688 see Tux comment

print $dataLength, "\n";
print "$type\n";
print "$version\n";
print "$rank\n";
print "$flags\n";
print "$serial\n";
print "$ttl\n";
print "$reserved\n";
print "$timestamp\n";
print inet_ntoa($data) . "\n";
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