This code works for me when I add this before your code:

use CGI;

my $q = CGI->new;
[download]

Sometimes you have to explicitly use parens with print, but your code seems fine to me. :/

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)