$result = $soap->createNewOrder(
[...]
SOAP::Data->name('Item' => \SOAP::Data->value(
 SOAP::Data->name('subItem1' => SOAP::Data->type(string => $subItem1[0])),
 SOAP::Data->name('subItem2' => SOAP::Data->type(string => $subItem2[0])),
 SOAP::Data->name('subItem3' => SOAP::Data->type(string => $subItem3[0]))    
)
[...]
)