Its a hash without a name of its own - e.g.

  my @list;

  # push an anonymous hash into @list 
  push @list, { apples => 'green', peaches => 'cream' };
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The hash is created using a pair of curlies, and then pushed straight into our list. The hash never has a name of its own, so you can only refer to it as a member of the list, e.g.

  $list[0]->{pears} = 'expensive';
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