use Digest::MD5 qw(md5_hex);
use Math::Prime::Util ':all';
...
$unique_offering = todigitstring(fromdigits(md5_hex($harvest), 16), 36);

##</code><code>##

$unique_offering = sub {
    require Digest::MD5;
    require Math::Prime::Util;
    return Math::Prime::Util->todigitstring(
           Math::Prime::Util->fromdigits(
           Digest::MD5->md5_hex($harvest), 16), 36);
    };