sub add_son_father_pair {
  my $name1 = ask_question("Enter a male name: ");
  if (exists $son_father{$name1}) {
     print "Duplicate name -- try again!\n";
     return;
  }

  my $add_dad = ask_question("Add a father: ");
  $son_father{$name1} = $add_dad;
}

sub ask_question {
   my $question = shift;
   print $question;
   chomp(my $answer = lc <STDIN>);
   return $answer;
}