There isn't a "built-in" subroutine called "lookupaddress" in perl. There are, of course, several different ways of performing DNS queries.

I'm guessing you got the idea about a sub called "lookupaddress" from the Perl for System Administration Book. In the book, they offered several different ways of creating the "lookupaddress" subroutine.

Here's one of them. It uses Net::DNS, which may be of interest to you.

# this is straight from the o'reilly book.
# the liberal use of globals is their idea, not mine :)
# It populates a global hash without returning it,
# and is probably only useful in the context of the book
# exercise -
sub lookupaddress{
    my($hostname,$server) = @_;

    $res = new Net::DNS::Resolver;

    $res->nameservers($server);

    $packet = $res->query($hostname);

    if (!$packet) {
        warn "Unable to lookup data for $hostname from $server!\n";
        return;
    }
    # stores the last RR we receive
    foreach $rr ($packet->answer) {
        $results{$server}=$rr->address;
    }
}
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