use feature ":5.12";

sub usage { die "Usage $0 <unix|linux|dos|win|mac|apple>\n" }
usage() if $#ARGV != 0;

my $eol;
given ($ARGV[0]){
	when ([qw(unix linux)]){ $eol =   "\n" }
	when ([qw(dos win)])   { $eol = "\r\n" }
	when ([qw(apple mac)]) { $eol = "\r"   }
	default { usage() }
}

binmode(STDIN);
binmode(STDOUT);

my $last;
while (sysread(STDIN, my $ch, 1) > 0) {
	if ($ch eq "\r" or $ch eq "\n"){ 
		syswrite(STDOUT, $eol) unless $last eq "\r" and $ch eq "\n";
	} else { 
		syswrite(STDOUT, $ch)
	}
	$last = $ch;
}