sub start_workflow {
    my ($self, $wf_task, $wf_user) = @_;

    my $userAgent = LWP::UserAgent->new(agent => 'perl post');
    my $xml = "<?xml version=\"1.0\" encoding=\"UTF-8\" ?> 
<SOAP-ENV:Envelope 
    xmlns:SOAP-ENV=\"http://schemas.xmlsoap.org/soap/envelope/\" 
    xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" 
    xmlns:xs=\"http://www.w3.org/2001/XMLSchema\">
    <SOAP-ENV:Body>
        <ns1:SAP_WAPI_START_WORKFLOW xmlns:ns1=\"urn:sap-com:document:sap:rfc:functions\">
            <TASK>$wf_task</TASK> 
            <USER>$wf_user</USER> 
        </ns1:SAP_WAPI_START_WORKFLOW>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>";

    my $response = $userAgent->request( POST $self->{__service},
                                    Content_Type    =>  'text/xml',
                                    Content         =>  $xml,
                                    Authorization   =>  $self->{__authorization}, );
                                    
    return $response->content;
}