I personally find that style of sql construction hard to read. How about this:

my $sql = do {
  my $getfields = join ',', @getfields;
  my $placeholders = join ',', ('?') x @choices;
  my $settingspublic = join ' OR ', map "settings$_ = 'public'", 1 .. 
+4;

  <<EOF;
  select $getfields
    from special_fields
    where engine in ($placeholders)
      and ($settingspublic)
EOF
};
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