my $complex_data_structure = {'a'=>[1,2,3], 'b'=>{'c'=>[4,5,6],'d'=>LWP::UserAgent->new()}};
my $serialised_data = Sereal::Encoder::encode_sereal($complex_data_structure);
$pfm->finish(0, \$serialised_data); # <<< note that we pass a reference to our serialised-data.