You're right, my bad. Despite allegedly supporting SQL::Statement::Syntax, in fact DBD::Sponge essentially ignores the statement and does a plain ol' SELECT *.... and the only use I can envision for that is as a bridge between your perl data and some black-box module which requires a statement handle.

The documentation of DBD::Sponge's prepare() is pretty unclear on this issue:

The $statement here is an arbitrary statement or name you want to provide as identity of your data. If you're using DBI::Profile it will appear in the profile data.

Generally it's expected that you are preparing a statement handle as if a select statement happened.

Anyway, sorry for the red herring.

Update: I checked into a couple of DBD modules which allow to access in-memory perl data structures as sources for DBI — DBD::AnyData and DBD::RAM (both, like SQL::Statement and other parts of the DBIverse, by jZed). Alas, neither supports GROUP BY!