How does CGI.pm handles Content-type: text/html\n\n ?

[LI NGOK LAM]

I have read throught the CGI::Carp::fatalsToBrowser.......
not quite understand all, but I wonder how does this script
handles the "Content-type: text/html\n\n"......
So in the some case s(such as warnings) this header line won't re-print ?

TIA