binmode STDIN or die $!;
binmode STDOUT or die $!;

C:\> perl dos2unix.pl < dostext.txt > unixtext.txt

C:\> perl dos2unix.pl dostext.txt > unixtext.txt   # klappt nicht!

my (@newLine) = &AnalyzeFileEol($infile);
my $newLine = join("", map { chr(hex($_)) } @newline;
local $/ = $newLine;

# ------------------------------------------------------------
sub AnalyzeFileEol {
    my ($file) = shift;
    my $eol = chr(10);

    unless (open (FH, "<", $file)) {
    die "Error: couldn't read file '$file': $!\n";
    } # unless

    my @chars = ();

    while (defined (my $chr = getc(FH))) {
    my $hex = sprintf("%02X", ord($chr));

    if ($hex eq '0D') {
        my $next = sprintf("%02X", ord(getc(FH)));

        if ($next eq '0A') { close (FH);
        print "Newline format: Dos: $hex $next\n";
        return ($hex,$next);
        } # if
         else { close (FH);
        print "Newline format: Mac: $hex\n";
        return ($hex);
        } # else
    } # if
    elsif ($hex eq '0A') { close (FH);
        print "Newline format: Unix: $hex\n";
        return ($hex);
    } # elsif
    } # while

    die "Error: couldn't find out file format\n";

    close (FH);
    return;
} # AnalyzeFile
# ------------------------------------------------------------

my (@newLine) = &AnalyzeFileEol($infile);
my $newLine = join("", map { chr(hex($_)) } @newline;
local $/ = $newLine;

# ------------------------------------------------------------
sub AnalyzeFileEol {
    my ($file) = shift;
    my $eol = chr(10);

    unless (open (FH, "<", $file)) {
    die "Error: couldn't read file '$file': $!\n";
    } # unless

    my @chars = ();

    while (defined (my $chr = getc(FH))) {
    my $hex = sprintf("%02X", ord($chr));

    if ($hex eq '0D') {
[...]

#!/usr/bin/perl
use strict;
use warnings;

my $filename = shift;

{
    local $/ = LineSeparator($filename);

    # mach was mit der Datei
}

exit 0;

############################################################

sub LineSeparator {
    my ($file) = @_;

    open (my $infile_h, '<', $file) or die "could not open '$file' for reading: $!";
    binmode $infile_h;
    my $eol = '';
    my $format = 'unknown';

    while (defined (my $chr = ord getc($infile_h))) {
        if ($chr == 0x0D) {
            $chr = ord getc($infile_h);
            if ($chr == 0x0A) {
                $format = 'DOS';
                $eol = "\x0D\x0A";
            } else {
                $format = 'MacOS 9 or earlier';
                $eol = "\x0D";
            }
            last;
        } elsif ($chr == 0x0A) {
            $format = 'UNIX';
            $eol = "\x0A";
            last;
        }
    }
    close $infile_h;
    print STDERR "Line terminator format: $format\n";
    return $eol;
}