update: whoops, read the note way too quickly. Thought you wanted a trace of what's going on in the prepare calls; the advice stands for that usage, but not for the poster's question!

Check out the DBI's trace method, which is simple to set up:

my $db = DBI->connect(#blah blah blah");
# trace level (1-9), and output (STDERR if not specified)
$db->trace(2, '/tmp/trace.log');
[download]

I find level 2 to be of general use while debugging harder problems, 3 when 2 doesn't reveal enough, but I've never needed to go any higher. As the docs used to say, 6 really is too high to be useful, but I suppose it's there for a reason =)

If not P, what? Q maybe?
"Sidney Morgenbesser"