The request processor doesn't have anything magical in this regard, and if it did, it'd just be a short cut for what you typed above. Perhaps a short wrapper proc (to make things read more cleanly?) along the lines of:
ad_proc append_outputheader {-overwrite:boolean key value} {
Add an output header that will get written to the client
connection. Use -overwrite to update a key that already
exists (without -overwrite a duplicate key results in
multiple headers being sent to the client which may very
well be OK depending on the header).
} {
if {$overwrite_p} {
ns_set update [ad_conn outputheaders] $key $value
} else {
ns_set put [ad_conn outputheaders] $key $value
}
}
