What is the correct form of response from a CGI script?
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The CGI specification allows any of the usual newline representations in the CGI response (it's the server's job to create an accurate HTTP response based on it). So "\n" written in text mode is technically correct, and recommended. NPH scripts are more tricky: they must put out a complete and accurate set of HTTP transaction response headers; the HTTP specification calls for records to be terminated with carriage-return and line-feed, i.e ASCII \015\012 written in binary mode.

Using CGI.pm gives excellent platform independence, including EBCDIC systems. CGI.pm selects an appropriate newline representation ($CGI::CRLF) and sets binmode as appropriate.