My only disappointment is that this is not a Perl-ish recipe for a mixed drink. :(

My only suggestion is to avoid using 'hard coded' hash keys and array indices. I prefer to use a while loop to gather STDIN instead of a for loop, but there are many, many different ways to do this. Here's my take on it:

use strict;
use warnings;

my %hash;
my @array;
my $key    = 'aa';
my $prompt = "\nEnter value <cntl-d exits>: ";

print $prompt;

while (<STDIN>) {
    chomp;
    push @array, $_;
    print $prompt;
}

$hash{$key++} = $_ for @array;

print "\n";
print "$_ contains $hash{$_}\n" for sort keys %hash;
[download]

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)