This is a SQL issue, not a DBI::CSV issue. DISTINCT only eliminates those rows where all of the selected fields are identical. You could eliminate more rows by specifying the GROUP BY keywords, but i doubt you really want to do that ... consider either normalizing your data or using a hash solution instead.

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)