Hey Plankton!!
Not necessarily the answer to your post, but here is my solution to essentially the same problem set you are dealing with. Perhaps you can adapt it accordingly?

I opted not to use WWW::Mechanize but use a straight up LWP::UserAgent approach and an HTML parser to achieve the same result you are after.

Just a thought...

Parsing the output of the Asante should be similar too.

#!/usr/bin/perl -w
######################################################################
+##
# Get External IP address of Netgear router
#################################################
use strict;
use warnings;
use LWP::UserAgent;
use Data::Dumper;
#use HTML::TableContentParser;
use Getopt::Long;

my $host="";
my $user="";
my $password="";
my $addr = "";
my $port=80;
my $Netgear_Page = "s_status.htm"; # Netgear Router status
my $Linksys_Page = "Status_Router.asp";
my $result=GetOptions(
                      "host=s" => \$host,
                      "user=s" => \$user,
                      "password=s" => \$password,
                      "ipaddress=s" => \$addr,
                      "port=i" => \$port
                   );
my $ua=LWP::UserAgent -> new();

if ($host){
}else{
  for (qx/ipconfig/){
    m/^\s+Default Gateway\D+([\d|\.]+)/ and $host=$1
  };
}

barf_and_complain()
    unless (
            $host and $user and $password

            );
my $host_settings=sprintf("%s:%d",$host,$port);
my $url = sprintf("http://%s:%d/$Netgear_Page",$host,$port);


my  $req = HTTP::Request->new(GET => $url);
$req->authorization_basic($user, $password);
my $content = $ua->request($req)->as_string;
##print "----Content--\n$content-----\n";
while ($content=~m/<table.*?>(.+?)<\/table>/igs){
   my $table = $1;
   ##print "----TABLE:$table\n\n";
   $table =~m/<h\d>(.+?)<\/h\d>/igs and print "=====TABLEHEAD: $1\n";
   for ("MAC Address",  "IP Address", "Domain Name Server"){
     $table =~m/<td.*?>$_.+?<\/td>\s*<td.*?>([\w|:|\.|<|>]+?)<\/td>/
         and print "\t $_ $1\n";
   }
}

sub barf_and_complain {

printf "%s\n",qq(
You must specify all options for this plugin to work:
                 --host hostname or ip of router
                 --user security user of router
                 --ipaddress expected ip address
                 --password  login password for router

                 the --port option is just that, an option and default
+s
                 to 80
                 );
exit(1);

}
[download]

• Try to guess internal IP of router - it should be your default gateway
• Get rid of HTML::TableContentParser
• Simplify parsing code
• Use Userid instead of realm