$|      If set to nonzero, forces a flush after every  write
             or  print  on the currently selected output channel.
             Default is 0.  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.
             (Mnemonic: when you want your  pipes  to  be  piping
             hot.)