sub cgi2args {
    my $cgi = shift;
    #my $cgi = CGI->new('a.b.c=3&a.b.c=4&x.y=4'); 
    # a & a.b ? warn
    my $args = {};
    for my $name ($cgi->param) {
    # could warn unrecognized for html typos
    #for my $name (grep $interface_re, $cgi->param) {
        my @segments = split /\./, $name;
        my $last_seg = pop @segments;
        my $a = $args;
        for (@segments) {
            $a->{$_} ||= {}; # XXX defined not true
            $a = $a->{$_};
        }
        my @values = $cgi->param($name);
        $a->{$last_seg} = @values == 1 ? $values[0] : \@values;
    }
    return $args;
}