Does MySql work on both Linux and Windows?
MySql now belongs to Oracle and as Mr. Ellison is hardcore commercial, the focus of MySQL is/will probably to push you towards some kind of paid license.
It doesn't matter very much what you'll put into the DB - the "what you want to do with it" is more important.
use "MariaDB", which is the open-source fork of MySQL.
(I think that I read on wikipedia that "My" was the name of the first child of the guy who created "MySQL" and "Maria" was the other child - or maybe I'm just stupid to believe that)
In any case the recommendation stands - I'm using it for some tables that hold a couple of million rows and it's working fine.
Use some abstract layer.
I used "PDO" with PHP and I didn't regret it.
I have no clue about Perl - from what I'm finding now you might want to use "PDI", just have a loook around.