Generally you should only call initscr once. The other problem is that you're calling erase followed by refresh. Your program should have this structure:

use Curses;

initscr();
while (1) {
  erase();
  ...draw new screen using addstr, etc....
  refresh();
  sleep(2);
}
endwin();
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refresh is where the screen is actually changed. erase and all the other drawing commands just change an in-memory copy of the screen.