You're real close. All you need now is an array to store the cloned balls. Put a line like this above the for loop:

   my @cloned_balls;

Then a line inside your loop to put the balls in the array. For example, using push():

   push(@cloned_balls, $relement);

Now you should be able bind them using the array of balls:

   $zinc->bind($cloned_balls[0], '<1>',  \&ro6b);

-sam