fun length [] = 0
   | length (head::tail) = 1 + length tail;


##</code><code>##


sub length {
    return 0 unless @_;
    # manual pattern matching of the array here
    my ($head, @tail) = @_;
    return 1 + length(@tail);
}


##</code><code>##


member (X, [])    -> false;
member (X, [X|_]) -> true;
member (X, [_|T]) -> member(X, T).


##</code><code>##


sub member {
    my ($X, $head, @tail) = @_;
    return 0 unless defined($head) && scalar @tail; 
    return 1 if $X == $head;
    return member($X, @tail) if $X != $head;
}