Um, no, "Content-type" does not have to go first. Actually, it usually comes last, if you look at the output from an apache server, for example. Both "content-type" and "content-length" are entity-header fields, and as such are on equal footing. Check out the HTTP RFC and you'll see that the order of the headers is not specified, but is recommended that the entity-header fields go last. Also, the examples in the RFCs all have "content-type" as the *last* header.

The script may be failing, but it's a protection or a binmode problem, not the headers.