If you want the output as array, you can use split and unpack, otherwise you can use pattern matching with /g flag in a while loop.
example with unpack & character by character processing

$string="Hello World";
$sum = 0;
foreach $ascval (unpack("C*", $string)) {
    $sum += $ascval;
}
print "sum is $sum\n";
# prints "1052"
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