Also, if you're starting out doing web application development, read "MySQL and Perl for the Web". That site contains a slick WebDB.pm that does
some input validation based on the MySQL table "metadata".
(read the book for explanation how to use it :) Actually
he (Paul DuBois) has a really excellent book called "MySQL"
(I used it to figure out how to do MySQL stuff from the
Apache C API, which made me feel special, hehe).