Thanks, in the meantime I'd realised that myself. Just in case it's useful to anybody else I include my code so far for asynchronous resolution. As far as I can see from the documentation retrieving records from the results should be as simple as traversing an array of arrays and picking out the bits you want. e.g. A or AAAA records.

#!/usr/bin/perl -w
use strict;
use warnings;
use Data::Dumper;
use AnyEvent::DNS;

my ($domain,$START_TIME,$MAX_QUERIES,$MAX_QUEUE,
    $time,$done,$resolved);
my (@domains,@condvars);

$START_TIME = time;
$MAX_QUERIES = 1000;
$MAX_QUEUE   = 10;
$resolved = 0;

# setup resolver
my $resolver = AnyEvent::DNS::resolver;
$resolver->max_outstanding($MAX_QUEUE);
#$resolver->timeout([0,1,2]);

while (1)
{
  # send dns packets
  for my $i (1..$MAX_QUERIES)
  {
    $domain = <>;
    # clean off newline
    chomp $domain;
    $resolver->resolve($domain,"*",my $condvar  = AnyEvent->condvar);
    push @condvars, $condvar; 
  }
  
  # receive dns packets
  while (my $condvar = pop @condvars)
  {
    $resolved++ if ($condvar->recv);
    #warn Dumper [$condvar->recv];
  }
  $done += $MAX_QUERIES;
  $time = time - $START_TIME;
  print "Done $done domains, $resolved resolved in $time seconds.\n";
}
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