derby points out the answer to your question, but there's another couple of pieces.
  1. If you want to process the file one line at a time, you need to set $/ anyway, or you may not be reading one line at a time.
  2. If you need to preserve the original line-endings for a write-out operation at some point, you can just easily modify the sub to set $\ as well.

Because of the first, the whole structure is kind of odd anyway, since with Mac line endings, you'd slurp the whole file to find out that you have those line endings.

Better to do: 

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 #
}

[download]

This is predicated on the text-files being well-formed (ending with an EOL before EOF), so you may need to handle the possibility of malformed files or whatnot.

<-radiant.matrix->
Larry Wall is Yoda: there is no try{} (ok, except in Perl6; way to ruin a joke, Larry! ;P)
The Code that can be seen is not the true Code
"In any sufficiently large group of people, most are idiots" - Kaa's Law

In reply to Re: alter $/ - but why? by radiantmatrix
in thread alter $/ - but why? by rvosa

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