initialize_variables();

my $is_time_to_exit = 0;
while (! $is_time_to_exit) {

  my $choice = choose_menu_item();

  if ($choice eq 'a')    { add_son_father_pair(); }
  elsif ($choice eq 'd') { delete_son_father_pair(); } 
  elsif ($choice eq 'e') { $is_time_to_exit = 1; }
  elsif ($choice eq 'g') { get_a_father(); }
  elsif ($choice eq 'o') { output_hash_neatly(); }
  elsif ($choice eq 'r') { replace_a_father(); }
  elsif ($choice eq 'x') { get_a_grandfather(); }
  else {
   print "Invalid choice, TRY AGAIN!\n";
  }
}
print "Come back again -- goodbye!";