I didn't say "query", I said "$query" - as in the variable you're passing in to $dbh->prepare().

The query you posted, "SELECT user_id, username FROM users WHERE purch_perm_id != 1 AND deleted != 1 ORDER BY username" has no placeholders, so you shouldn't be binding anything.

Then the next place to look is where you're doing your binding.

  @dsetcols=[];
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I don't think this is doing what you think it's doing. It might be, I'm not entirely sure. This is setting @dsetcols to be an array with one element: an arrayref. You probably want:

  @dsetcols=();
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which sets @dsetcols to an empty array. Next you do:

  @fieldnames = split(/,/, $fnames);
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So, when your code fails, what is $fnames? Print that out in your error message, too. I would expect that your example query doesn't have a blank $fnames, even though it should.