Add default system newline in Perl - linux

Question

When I append text to a file I would like to add the correct line ending for the file: for Unix: "\n" and for Windows "\r\n". However, I could not find an easy way to do this. This was the best I could come up with:
use strict;
use warnings;
use Devel::CheckOS ();
my $fn = 'file';
open (my $fh, '<', $fn) or die "Could not open file '$fn': $!\n";
my $first_line = <$fh>;
my $len = length $first_line;
my $file_type = "undetermined";
if ($len == 1) {
$file_type = "Unix" if $first_line eq "\n";
}
if ($len >= 2) {
if (substr($first_line, $len - 1, 1) eq "\n") {
if (substr($first_line, $len - 2, 1) eq "\r") {
$file_type = "DOS";
} else {
$file_type = "Unix";
}
}
}
close $fh;
if ($file_type eq "undetermined") {
$file_type = get_system_file_type();
}
print "File type: $file_type.\n";
sub get_system_file_type {
return Devel::CheckOS::os_is('MicrosoftWindows') ? "DOS" : "Unix";
}
Is it really necessary to do all these checks? Or are there simpler ways to do this?

Answer 1

Use the :crlf handle, for example with use open and use if:
use if ($^O eq "MSWin32") => open qw(IO :crlf :all);
The relevant documentations:
PerlIO for the io layers. Note that this page states:
If the platform is MS-DOS like and normally does CRLF to "\n" translation for text files then the default layers are :
unix crlf
So the above code should be redundant, but that's what you're asking for.
perlvar for the $^O variable.
open for the open pragma.
if for conditional loading of modules.