• Repeatedly doing hash lookups is slower than doing it once
• The order appears reversed since as is you can't have two ads with the same weight nor lookup the weight of an add.

#!/usr/bin/perl
use strict;
use warnings;

my $lookup;
my %hash = split /:/ , '43:17:21:33:19:23:6:27';
while (my ($key, $val) = each %hash) {
    $lookup .= pack("C*", ($key) x $val);
}
print unpack("C", substr($lookup, rand 100, 1));
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