SQL::Statement doesn't handle subqueries or CASE statements. I welcome the help of anyone who would like to help add such support. AFAIK, it does currently support C-style comments when they occur at the start or end of a statement, but not when embedded in a statement. I intend to add support for embedded comments soon.

In terms of other modules that cover the same problem space, SQL::Translator has excellent support for DDL but not for SELECT statements; SQL::Routine is intdended to parse SQL but I'm not sure whether it can yet; DBIx::MyParse is a very promising looking module though I haven't tested it yet - it uses an embedded version of MySQL to give the parser a very robust (though MySQL specific) parser.