Random tip. I prefer to use the qq{} syntax so that the interpolated string doesn't stick out from my code. I also have a slightly different standard for writing SQL. So a basic example could look like this:

my $sth = $dbh->prepare(qq{
  select
      tbl.column1
    , tbl2.column2
  from tbl1
    join tbl2
      on tbl1.tbl2_id = tbl2.id
  where condition = ?
    and condition2 = ?
}) or die "Can't prepare query: $DBI::errstr";
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The basic idea being that continuation pieces like "," and "and" go in front of the next line rather than trailing on the previous line. The point being that when you go to change your SQL you're likely to add columns and/or conditions, and with my way of arranging things you avoid the annoying error where you insert a bunch of rows but forgot to add the continuation piece just before your insert.

You don't have to do things that way, but if you write as much SQL as I do, you'll find that it makes sense.

Update: zwon pointed out that I missed the qq{} in the code even though I had just talked about it. D'oh, fixed.