open F, '<', 'e:\hugefile' or die $^E;
binmode F;
$file = do{ local $/=\(100*1024*1024); <F> };
print length $file;
104857600

print scalar localtime; 
for( my $i=0; $i< (100*1024*1024); $i+=16 ) { 
	print $i if substr($file, $i, 16) eq ("\xff" x 16) 
}; 
print scalar localtime;

Sun Oct 19 16:00:32 2003
Sun Oct 19 16:01:21 2003