This works under modern Apache, but under older Apache versions, the script also had to be named nph-something to turn off the buffering. Consider the name as a signal that Apache should do its own $| = 1 equivalent.

The other things that older Apache required was that these "NPH" scripts provide the first HTTP status line as well, since Apache essentially stepped out of the way entirely. I think this is still true for scripts named like this as a backward compatiblity.

-- Randal L. Schwartz, Perl hacker