In your script you can use:

STDOUT->flush;

to flush the output buffer.

You can even set STDOUT->autoflush(1); globally

In your script you can use:

STDOUT->flush;

to flush the output buffer.

You can even set STDOUT->autoflush(1); globally.

To flush on newlines only try:

STDOUT->autoflush(0);
open STDOUT, ">/tmp/script.out"
.
.
close STDOUT;