$| affects the currently selected file handle (normally STDOUT). 

$|++;

[download]

is a weird way of saying 

$|=1;

[download]

and it's equivalent to 

select()->autoflush(1);

[download]

But when acting on the same file handle, $|=1; and ->autoflush(1) are equivalent.

In reply to Re^4: Daemon problem with sleep() by ikegami
in thread Daemon problem with sleep() by MichaelMeyer

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