my %refitems;
my $refitem = $zinc->add('arc',$centergroup2, [ [10,20], [20,30] ],
               -filled => 1,
               -fillcolor => $refgrad,              ##    $refgrad
               -linewidth => 0,
               -priority => 100
              );

# make/clone 11/12 more of the above
for (1..11){
   $refitem{$_} = $zinc->clone($refitem);
   $zinc->rotate($refitem{$_},.53*$_);
   #here you bind each one separately, and/or
   #pass extra info to the callback 
   $zinc->bind( $refitem{$_}, '<1>',  [  \&ro6, $_  ]    ) ;  
}