Sockets are bidirectional, so just print out the output back to the socket. Of course, system doesn't actually return the output, so you'll need something else.

my $client_sock = $sock->accept();
while(<$client_sock>){
   chomp;
   print $client_sock `$_`;
}
[download]

You'll need to add some kind of system to allow the client to know when the server is done sending.

Are you just exploring, or are you reinventing ssh?