in reply to Streaming to Handles

If what you're doing is fork-friendly (i.e. doesn't involve modifying global variables), Perl has a built-in syntax just for you -- with open. (This sort of thing, by the way, is why I occasionally reread the perl PODs.) 
  #foo() is the sub that outputs a lot of data
  my $pid = open(SUBOUT, '-|');
  defined($pid) or die "Fork failed: $!";
  if ($pid == 0) { 
    $|=1; foo(); exit(0);
  }
  while (<SUBOUT>) ...

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The open will fork your script, and the forked copy (the one that calls the function) will have its STDOUT piped to the filehandle given to open() (in this case, SUBOUT).
Here's a quick example I crafted: 
#!/usr/bin/perl -l
defined($tmp = open(FOO, '-|')) or die "Can't fork: $!";

if ($tmp==0) {
        print "Roses are red\nViolets are blue\nI think Perl rules\nAn
+d you should too\n";
        exit(1);
}

print for map {chomp; "[$tmp] {$_}"} <FOO>;

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--Stevie-O 
$"=$,,$_=q>|\p4<6 8p<M/_|<('=>
.q>.<4-KI<l|2$<6%s!<qn#F<>;$,
.=pack'N*',"@{[unpack'C*',$_]
}"for split/</;$_=$,,y[A-Z a-z]
         {}cd;print lc

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In Section Seekers of Perl Wisdom