my @getfields = qw/engine/;
for my $type ( qw/name lable settings/ ) {
    for my $num ( 1 .. 4 ) {
        push @getfields, "$type$num";
    }
}
my $sql = 'select '.
          join( ',', @getfields ).
          ' from special_fields WHERE engine IN ('.
          join( ',', ('?') x scalar @choices ).
          ') AND ('.
          join( ' OR ', map { "settings$_ = 'public'" } 1..4 ).
          ')';

my $sth = $dbh->prepare( $sql );
$sth->execute( @choices );