In the context of your code, @ref01 is better written as $ref01.

You can make use of the flexibility of referencing and dereferencing to re-write

 foreach $i (sort keys (%{$ref01[0]})) {
  print "$i: ${$ref01[0]}{$i} ${$ref01[1]}{$i} ${$ref01[2]}{$i}\n";
  }
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in a briefer and yet robust way. you don't want to index a hundred-element array manually now, do you?

foreach $i (sort keys (%{$ref01})) {
        print "$i: @{$ref01->{$i}}\n";
        }
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An interesting documentation page is perlcheat at http://perldoc.perl.org. You can access the same from your command console, type perldoc perlcheat.

Best of luck and have a nice perl journey ..