I didn't step through the logic of the whole program but this looks rather suspect:

my @PromoterLenghts = (4);
my $PromotroListLength = $#PromoterLenghts;
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It looks like you want to set the first array to have four empty elements. What you are actually doing is setting the array to have its first element equal "4".

$PM = "Perl Monk's";
$MCF = "Most Clueless Friar Abbot";
$nysus = $PM . $MCF;