use strict;
use warnings;

my %eols=(
  unix  => "\x0A",
  linux => "\x0A",
  dos   => "\x0D\x0A",
  win   => "\x0D\x0A",
  mac   => "\x0D",
  apple => "\x0D",
);

sub usage ()
{
  print STDERR "Usage $0 ".join('|', sort keys %eols)."\n";
  exit(8);
}

sub determin_eol($$)
{
  my ($last,$ch)=@_;
  my $write='';
  # Win Ending
  if($last eq "\x0D" && $ch eq "\x0A")
  {
    $write=$eol;
    $last='';
  }
  # Mac Ending
  elsif($last eq "\x0D")
  {
    $write=$eol;
    $last=$ch;
  }
  # UNX Ending
  elsif($last eq "\x0A")
  {
    $write=$eol;
    $last=$ch;
  }
  # no ending found
  else
  {
    $write=$last;
    $last=$ch;
  }
  return ($write,$last);
}

binmode(STDIN);
binmode(STDOUT);

usage() unless (@ARGV && $eols{$ARGV[0]});

my $eol=$eols{$ARGV[0]};
my $ch;
my $last='';
while (sysread(STDIN, $ch, 1) > 0)
{
  my $write='';
  ($write,$last)=determin_eol($last,$ch);
  syswrite(STDOUT, $write);
}
# write last char.
syswrite(STDOUT, join('',determin_eol($last,'')));