Autoflush the buffer. This is directly from perlvar:
If set to nonzero, forces a flush right away and after
every write or print on the currently selected output
channel. Default is 0 (regardless of whether the channel is
actually buffered by the system or not; $| tells you only
whether you've asked Perl explicitly to flush after each
write). Note that STDOUT will typically be line buffered if
output is to the terminal and block buffered otherwise.
Setting this variable is useful primarily when you are
outputting to a pipe, such as when you are running a Perl
script under rsh and want to see the output as it's
happening. This has no effect on input buffering.
(Mnemonic: when you want your pipes to be piping hot.)
So, try $|++
or $| = 1
. Both will turn on autoflushing,
but I tend to like $| = 1
better since it is less cryptic for novices.