I agree with the other posts that the / should be in place of the \ mark. You also never used the path of the file. I've run some FTP scripts of my own. I did it this way :
$host = "servername";
$user= "username";
$pw = "password";
$ftp = Net::FTP->new("$host", Debug=>0);
if($ftp){
$ftp->login($user, $pw);
$ftp->cwd("directory_path/subdirectory/here");
$ftp->get("filename_in_directory");
}