my %document = (
    '1' => {
        '1.1' => 'xxx',
        '1.2' => {
            '1.2.1' => 'xxx',
            '1.2.2' => 'xxx'
        }
    },
    '2' => {
        '2.1' => {
            '2.1.1' => 'xxx'
        }
    }
);


##</code><code>##



sub process (%chapters) {
    await do for %chapters.kv -> $number, $content {
        start {
            note "Chapter $number started";
            &?ROUTINE.outer.($content) if $content ~~ Hash;
            sleep 1; # here the chapter itself is processed
            note "Chapter $number finished";
        }
    }
}
process(%document);