I agree with ichimunki, the code we see looks good, but either you're getting a funky value for $s (whitespace or not alphabet character) or %alphabet doesn't really have in it what you think it does.

I'd recommend adding a couple of sanity check statements right before your modulus test:

# what's in the %alphabet?
foreach my $letter (keys %alphabet)
{
  print "$letter\n$alphabet{$letter}\n";
}
# what's $s?
print "$s\n";<br>

# does a key/value pair exist in %alphabet for $s?
print "$alphabet{$s}\n";<br>
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~CubicSpline
"No one tosses a Dwarf!"