You just need to put a reference to the AV in the HV. (notice the newRV_inc()) The following code is untested (I don't have a compiler on this computer) but should give you the right idea. 
AV * array = newAV();
HV * hash = newHV();

// use AV_store() to put something in the array

HV_store(hash, "key3", 4, newRV_inc((SV *) array), 0);

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In reply to Re: XS Storing AV in HV entry by SarahM
in thread XS Storing AV in HV entry by Anonymous Monk

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