Perl: additional ctx->header_sent checks. As we now have ctx->header_sent flag, it is further used to prevent duplicate $r->send_http_header() calls, prevent output before sending header, and $r->internal_redirect() after sending header. Further, $r->send_http_header() protected from calls after $r->internal_redirect().

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


cat << END >> $NGX_AUTO_CONFIG_H

#ifndef $have
#define $have  1
#endif

END