Transactions give you many things. Isolation, duration, etc. But there is more missing from MySQL. Safe on-line backups. (No, just backing up the filesystem with the tables will not do if you want to keep data consistent). Triggers. Integrety checks. Nested queries.

I strongly suggest reading http://openacs.org/philosophy/why-not-mysql.html. Only use MySQL if you truly understand the dangers.

Finally, the O'Rielly Perl DBI book is very good, but DBI isn't that complicated.

Most certainly. However, writing good SQL queries can be an art in itself. Many queries are simple, but when they get more complicated it's easy to write something that runs for 24 hours, while it could have been done in 5 minutes.

Abigail, DBA in several former lives.