my @nums = (
    0x000000,
    0x010000,
    0x020000,
    0x030000,
);

++$nums[-1];

printf("0x%05X\n", $nums[-1]);

##</code><code>##

my @formatted_nums = (
    '0x000000',
    '0x010000',
    '0x020000',
    '0x030000',
);

$formatted_nums[-1] = sprintf("0x%05X\n", hex($formatted_nums[-1]) + 1);

print("$formatted_nums[-1]\n");