• You are opening OUT for read, it shoud be open OUT, ">$file";
• The file name for OUT is the same as the flie name of IN, you will find that you clobber the contents on $file before you do anything

Open a tempory file, say "$file.tmp", write to that and then rename it to $file

Put

use strict;
use warnings;
[download]

Check you open the file handle

open IN, $file or die "Can't open $file: $!\n";
[download]