To make up for my oversight, here is another way to do it:

use Math::Matrix;

# ... yadda yadda

my $matrix = Math::Matrix->new(@array);
my $rows   = [ 
   map {{ 
      cells => [ map {{ data => $_ }} @$_ ]
   }} @{$matrix->transpose}
];
[download]

jeffa

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)