my %options = (
    rows=> 100,
    "facet"=> "on",
    "facet.field"=> "author_id",
);
use Data::Dumper;
my $response = $solr->search("\*:\*", \%options);

my $data = Dumper(\$response);
my %facet;
if($data =~ m#"facet_fields":{\s*"author_id":\[\s*([^\]]+)\]},#i){
  my $authors = $1;
  while($authors =~ m#"([^"]+)",(\d+),#gi){
        $facet{$1} = $2;
  }
}