in reply to Tricks with DBI

my($id, $name, $phone); $sth->bind_columns(undef, \$id, \$name, \$phone);
A shorter way is:
$sth->bind_columns(\my ($id, $name, $phone));
And regarding this statement:

And, for the same reasons, you should use prepare_cached instead of prepare.

Choosing prepare or prepare_cached really depends. The caching is a slight overhead, so if I can reasonably arrange my SQL so that something is only prepared once (or if its used just once anyway), then I'll just use 'prepare'. Or if you're dynamically creating a SQL statement (lets say a million times) and the number of possible unique combinations is large, then you don't want to use prepare_cached, e.g. you have a couple of 'IN' clauses, and each one might have 1-100 elements, so you end up with something like:

select stuff from table where field1 in (?,?,?,?) and field2 in (?,?,?,?,?)
(Note: placeholders are still a good idea in this case)