open IN, '<', $filename or die ("Can't open $filename: $!");
sysseek IN, -5, 2;

my $last_five;
sysread IN, $last_five, 5;

## find out what the EOL chars are and set $\ to match
$/ = $1 if $last_five =~ m/(\r{0,1}\n)$/s;

sysseek IN,0,0;
while (<IN>) {
   chomp;
   # now process stuff #
}