Apache Reference: mod_asis
mod_asis - Generation of Raw Responses
Since Apache 1.0, src/modules/standard/mod_asis.c
The Apache Group (1995)
mod_asis allows file types to be defined so that Apache will send them as is, without adding HTTP headers. It can be used to send any kind of data from the server, including redirects and other special HTTP responses, without the use of a CGI program.