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);


##</code><code>##

{ hk1 => 5, hk2 => [[21], [100 .. 104, 120, 23]] }
{
  hk1 => 5,
  hk2 => [
           [21, "01", "02", "03", "04", "05", "06", "07", "08", "09", 10],
           [100 .. 104, 120, 23],
         ],
}