btrott's answer is correct. If you are not using mod_perl or Apache::SIG (i.e. you don't have any control over the webserver used) Then you have to catch SIGPIPE on stdout. Set up your program to do this and you should be ok. Basically, you just have to catch the signal on the perl side of things before the web server's handler does the work for you.
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Crulx
crulx@iaxs.net