
   %hash = (apple => 'red',
            banana => 'yellow',
            kiwi => 'brown');
   @keys = keys %hash;
   print "keys: @keys.\n";

   delete $hash{banana};
   @keys = keys %hash;
   print "keys after deleting 'banana': @keys.\n";


   undef $hash{kiwi};
   @keys = keys %hash;
   print "keys after undef-ing 'kiwi': @keys.\n";


