What you are trying to do is less than totally clear from the question you asked, but I think the solution you found and posted subsequently cleared it up somewhat. From my point of view there are only two possibilities of what you are trying to do:

1. POST some XML as a parameter of a form, e.g. some XML that was pasted or typed in a HTML <input type="text"> or <textarea> widget.
2. POST some XML as the body of a HTTP request, with a Content-type header of text/xml (or whatever). This is a perfectly legitimate thing to want to do, particularly if you are building a RESTful web service.

It seems pretty clear from your answer that what you're talking about is no. 2. Care to comment?

While this is an aside (because you got the POST over HTTPS to work and that's probably all that matters to you), I feel compelled to point out that what you're posting isn't XML, it appears to be a string "CLRCMRC_XML=$finalXML", for whatever value of $finalXML. This makes the semantics of the HTTP request quite unclear; the Content-type header is blatantly misleading (or even just 'wrong').

You mightn't give a rat's ass about this because the semantics are in your brain; nonetheless I think I would just give that a mime type of plain text or something in the Content-type header.