my $cr = chr(0x0d);
my $lf = chr(0x0a);
my $infile = "test.txt";
open (IN, "<$infile") or die "Couldn't open input file: $!";
my $first_line = <IN>;
my ($line_text, $line_ending) = ($first_line =~ /(.*)(\015|\012|\015\012)/);
# detect line ending type
if ($line_ending eq "$cr$lf") {
  print "Windows line ending\n";
} elsif ($line_ending eq "$lf") {
  print "UNIX line ending\n";
} elsif ($line_ending eq "$cr") {
  print "Mac line ending\n";
} else {
  print "Unknown line ending\n";
  }
close (IN);