use strict;
use warnings;
use Data::Dump qw(dump);

my $data = {
    'hk1' => 5,
    'hk2' => [
        [21],
        [100, 101, 102, 103, 104, 120, 23]
    ]
};

print dump($data), "\n";
push @{$data->{hk2}[0]}, "01" .. "10";
print dump($data);