I don't like they put facet field and facet count in one array,

So, just hashify it yourself (although you'll lose the sorting, of course):

my $autId = $facet_counts->{facet_fields}{author_id};
my %easy_hash = @$autId;
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maybe my "Dumper +Regex" is safer.

Almost certainly not. Take the robust approach and then post-process the data as desired.