#!/usr/bin/perl
use strict;
use warnings;
						
open my $ogg_file, '<', shift or die $!;
binmode($ogg_file);

read_ogg_header($ogg_file);

sub read_ogg_header {
	
	my ( $file ) = @_;
	
	read($file, my $buf, 28 );

	my ( $ogg_magic, $ogg_version, $flags, $granule_position, $serial_number, $sequence_number, $checksum, $total_segments, $segment_size ) = unpack('C4 C1 C1 C8 C4 C4 C4 C1 C1', $buf);

    print $ogg_magic;  ### Expected it to print 'OggS'
}

##</code><code>##

0x4F6767530002000000000000000083CA3DC0000000009F59730A0113