sub do_msalist {    
   my (%country, %state, %msaname, @msakeys);

   sub by_americentric {    
      $country{$b} cmp $country{$a}  or
      $state{$a}   cmp $state{$b}    or    
      $msaname{$a} cmp $msaname{$b}  or    
      $a <=> $b
   }
 
   foreach (sort by_americentric @msakeys) {
      ...
   }
}