request.xml

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ns="http://services.muhimbi.com/2009/10/06" xmlns:ns1="http://types.muhimbi.com/2009/10/06" xmlns:ns2="http://types.muhimbi.com/2010/05/17">
   <soapenv:Body>
      <ns:GetDiagnostics>
         <ns:convertersToDiagnose>
            <ns1:DiagnosticRequestItem>
               <ns1:ConverterName>WordProcessing</ns1:ConverterName>
            </ns1:DiagnosticRequestItem>
         </ns:convertersToDiagnose>
      </ns:GetDiagnostics>
   </soapenv:Body>
</soapenv:Envelope>

script.pl

use SOAP::Lite +trace;
use warnings;

my $client = SOAP::Lite
  ->readable(1)
  ->uri("http://services.muhimbi.com/2009/10/06")
  ->proxy("http://ms.onehub.com:41734/Muhimbi.DocumentConverter.WebService/")
  ->ns("http://services.muhimbi.com/2009/10/06", 'ns')
  ->ns("http://types.muhimbi.com/2009/10/06", 'ns1')
  ->ns("http://types.muhimbi.com/2010/05/17", 'ns2');

my $method = SOAP::Data->name('GetDiagnostics' => \SOAP::Data->value(
        SOAP::Data->name('convertersToDiagnose' => '123')));

print $client->call($method)->result;