All you need to do is use an array instead of a scalar:

my @choice= $q->param("choice");
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foreach my $choice (@choice) {
   # do something with this $choice;
}
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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)