try changing that to a single q like
$sql = q~

I doubt that it will help much, but try it anyway. You don't need to worry about perl misunderstanding @-strings as arrays inside your sql.

As it won't interpolate the variables you wanted it to interpolate anyomore, also change all the $settings[...] to a simple ? in all occurrences and add the Array to the excute statement like this:
$sth2->execute( @settings );

Cheers, Sören