This is how I did it... Not your code, but a worthy example.

use XML::Parser;
....
Build your request and get response..
...
my $response = $userAgent->request($request);

Put the response in the XMLparser.

my $ref = XMLin($response->content);

my $secr = $ref->{'soapenv:Header'}->{'wsse:Security'};

print $secr;
[download]

I hope that guides you. :)