Modifying Set-Cookie header in Squid 3.3.9

[Peter Belau]

I'm trying to modify the Set-Cookie header from within client_side_reply.cc. 
Currently my code looks like this:

    HttpReply *rep = http->storeEntry()->getReply()->clone();
    http->storeEntry()->releaseRequest();
    rep->header.putStr(HDR_SET_COOKIE, "FOO=bar");
    http->storeEntry()->replaceHttpReply(rep);
    http->storeEntry()->complete();

This seems to corrupt storeEntry in ways that I don't understand. I imagine 
that I'm missing something fundamental here. If someone could point me in the 
right direct, I would much appreciate it.

Thanks,

Peter