If the server, username and password aren't changed very often, you might just try simplifying it down to:

#!/usr/bin/perl -w
use strict;
use Net::FTP;
my $ftp = Net::FTP->new('216.74.109.245') or die "Server not found";
$ftp->login('username','password') or die $ftp->message();
#$ftp->binary();
$ftp->ascii();  # you probably want to send it as ASCII instead of bin
+ary if it is a text file
$ftp->cwd("/public_ftp") or die $ftp->message();
$ftp->get("mystuff.txt") or die $ftp->message();
$ftp->quit;
[download]

You will see that I removed the variables that you were using only once. I also let the Net::FTP session provide it's own error messages.