sub _joiner {
    my $op = shift;
    my $filter = shift;
    while (my $cond = shift) {
        $filter = "($op $filter $cond)";
    }
    return $filter;
}

my $filter = AND(
    "(a=1)",
    IGNORE(
        "(b=1)",
        "(b=2)",
    ),
    "(c=1)",
);