use strict;
use warnings;

binmode STDOUT, ":utf8";
use utf8;

use JSON;

my $json ={
    'book' => [
        {'title' => 'smth'},
        {'num_page' => 234}
    ]
};
open my $fh, ">", "data_out.json";
print $fh encode_json($json);
close $fh;