When adding +trace, as documented in SOAP::Trace, I get the following XML, which seems to be close to your "working" XML:

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope
    soap:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
    xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
    xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <soap:Body>
    <RequestCircuitInfoByCircuitDesignId>
      <UserId xsi:type="xsd:string">xxx</UserId>

      <SubType xsi:type="xsd:string">CONTACTMASTERINFO</SubType>

      <CircuitDesignId xsi:type="xsd:long">5633874</CircuitDesignId>
    </RequestCircuitInfoByCircuitDesignId>
  </soap:Body>
</soap:Envelope>
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If this XML doesn't work, find out the differences and then (re)read SOAP::Lite to find out how to make SOAP::Lite send the appropriate XML.