score:4
PTY is an extremely simple airport for transit. There's no separation of departing and arriving passengers, so you literally go directly from your arrival gate to your departure gate. As long as you don't go downstairs to immigration you won't even see them. Just get off the first plane, check a departure board for your gate number, and go directly to it.
I should also note that at the time of writing the new Terminal 2 is partly open. There is an airside walkway (complete with PTY's first moving walkways) between the terminals, and all the gates in both terminals have been renumbered. So check the signs, even if you've been there before.