#!/usr/bin/perl 
use strict;
use warnings;
use File::Temp qw/ tempfile /;
use File::Copy;

my ($out, $filename) = tempfile("$ARGV[0]_XXXX", UNLINK => 0);

open my $in, '<', $ARGV[0] or die "Open failed: $!";

while (defined(my $line = <$in>)) {
    $line =~ s/\r\n/\n/;
    print $out $line;
}

close $in;
close $out;
move($filename, $ARGV[0]);