If you want something that never runs out, or can't be overfilled.

#!/usr/bin/perl
use warnings;
use strict;

$|++;

open(RH, "/dev/urandom") or die "$!\n";
#always some to read
#while (<RH>){print "$_\n";}

open(ZH, "> /dev/zero") or die "$!\n";
#can always write to it

while (<RH>){
  print "chunk";
  print ZH "$_\n";
}
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