I cleaned it up a little, then I tried this:

#!/usr/bin/perl

use strict;
use warnings;
use Net::SFTP::Foreign;

my $sftp = Net::SFTP::Foreign->new(
    'user@localhost',
    password => 'password',
    more     => ['-v']
);

$sftp->get('/remote/Desktop/copy', '/home/user/Desktop/copy')
  or die "unable to retrieve copy: ".$sftp->error;
[download]

This worked for me.