Originally posted by http://perldoc.perl.or g/perlvar.html
HANDLE->autoflush(EXPR )
$OUTPUT_AUTOFLU SH
$|
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 really buffered by the system or not; $| tells you only whether you've asked Perl explicitly to flush after each write). 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 or socket, such as when you are running a Perl program under rsh and want to see the output as it's happening. This has no effect on input buffering. See getc for that. (Mnemonic: when you want your pipes to be piping hot.)
Always try perldoc first for your questions about the internals of perls. It's likely to get you more information. And even more importantly, more accurate information.
Comment