Clearly a lot of work and talent has gone into the Genezzo database project. It is a SQL-compatible relational database written entirely in Perl. It is highly portable, and probably more extensible than any other database ever written. It is also open source, and as such you are invited to download the code, build it, test drive it, add your own code or extensions, or just shoot the bull on the Genezzo forum. Don't be shy.