HOW TO GET CPU USAGE IN BigIP::iControl ?

http://search.cpan.org/~ltp/BigIP-iControl-0.097/lib/BigIP/iControl.pm

hi,friends: i want to get the cpu usage by the method that's get_cpu_usage_extended_information_stringified...but it is error!

500 Internal Server Error at /usr/lib/perl5/site_perl/5.8.8/BigIP/iControl.pm line 599

the code :

 !/usr/bin/perl

use warnings;
use strict;
use BigIP::iControl;
use Data::Dumper;

my $ic = BigIP::iControl->new(
                                server          => '10.1.1.1',
                                username        => 'admin',
                                password        => 'abc123',
                                port            => 443,
                                proto           => 'https'
                        );

my $cpu=$ic->get_cpu_usage_extended_information_stringified();
print (Dumper($cpu)."\n");

[abc@localhost F5iControl]$ perl GetConfig.pl 
500 Internal Server Error at /usr/lib/perl5/site_perl/5.8.8/BigIP/iControl.pm line 599
[abc@localhost F5iControl]$ 

can u help me ?? ths...