Use parens to construct a hash, not curlies:

my %hof = (
          'key' => {
                     'innerkey2' => [
                                      'here'
                                    ],
                     'innerkey3' => [
                                      'there'
                                    ],
                     'innerkey1' => [
                                      'hello',
                                      'world'
                                    ]
                   }
        );
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The curlies are used to construct a reference to a hash.