sub in_list_recursive {
    my ($lsa,$lsb) = @_;
    if (@$lsa == 0) {
        return 1; # yay

    } elsif (@$lsb == 0) {
        return;   # nay

    } elsif ($lsa->[0] == $lsb->[0]) {
        shift @$lsa;
        shift @$lsb;
        return in_list_recursive( $lsa, $lsb );

    } else {
        shift @$lsb;    
        return in_list_recursive( $lsa, $lsb );
    };
};