ServiceStack implement magic token in deserializer

ServiceStack implement magic token in deserializer

I want to implement a magic token for my ServiceStack-based API. Whenever
any value matches this special token, I'd like to signal special actions
in my application. The ideal place for this assignment to occur would be
after SS had processed the wire format (JSV, JSON, SOAP, etc.) and before
it mapped the value onto the a .NET type. At the moment, I'm wondering
about the best way to start on something like this. Is it something I
could wire up in Configure()? Is it something I'll have to override and
inject? Any assistance or direction in this matter would be appreciated,
ASAP.