As an example, after running some perl code and retrieving the returned SV off the stack, I can extract a long value from it by running:

long value = SvIVx( thesv );

If I want to pass the long value back to my perl program, I can put it inside an SV by running the following:

SV* newsv = newSViv(long_in);

Same goes for double and string values. It is relativelly easy to extract them form the SV, pass it along to other programs, and then put it back into an SV.

No idea how to do the same for a reference, RV.

Greg