Linux

use strict;     
use Net::FTP;

my $host = "my.server";
my $user = "user";
my $password = "password";

my $f = Net::FTP->new($host) or die "Can't open $host\n";
$f->login($user, $password) or die "Can't login to $user in\n";

my $dir = "my/dir";

$f->cwd($dir) or die "Can't change working directory to $dir\n";

my $file_to_put = "filea";
my $file_to_merge = "fileb";
$f->binary();
#use this to put  filea to server
$f->put($file_to_put) or die "Can't put $file into $dir\n";
$f->append($file_to_merge, $file_to_put);
$f->quit;