I grappled with a similar problem, helped by monks. The first thread of interesting advice is here. At the end of that my conclusion was to use the following sledgehammer:

$dbh->do("LOCK TABLES tbl WRITE");
$dbh->do("$various_sql_stuff_without_getting_tangled");
$dbh->do("UNLOCK TABLES");
[download]

to crack a nut. Which I found works.

Then I mentioned this in another thread and htoug said some very interesting things, which to my shame I have not yet followed up; but when I revisit the MySQL aspects of my current project I shall try to slim them down, using his advice.

When I do that, I shall of course return to this thread too, where I confidently expect to find the optimal synthesis of former wisdom.

§ George Sherston