Use multi-level data structures instead. Do something like:

my %Categories = (
   cat1 => [
      'a', 'b', 'c',
   ],
# etc...
);

foreach my $sub_category (sort keys %Categories) {
   print $sub_category, $/;
   foreach my $value (@{$Categories{$sub_category}}) {
      print "\t$value\n";
   }
}

__END__
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