Slightly simplified and tweaked...

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1146579

use IO::Select;
use strict;
use warnings;
$| = 1;

my $children = 1000;
my $sel = IO::Select->new;
my $parentid = $$;

for my $i (1..$children)
  {
  if( open my $fh, '-|' )
    {
    $sel->add($fh);
    }
  else # child
    {
    print "Child Created: $$\n";
    for (1..10)
      {
      select undef, undef, undef, 2 + rand 0.1;
      printf "[%d] %5.2f\n", $$ - $parentid, rand 100;
      }
    exit;
    }
  }

while( $sel->count )
  {
  for my $fh ( $sel->can_read )
    {
    if( sysread $fh, my $buf, 4096 )
      {
      print "[parent] $buf";
      }
    else
      {
      $sel->remove($fh);
      }
    }
  }
print "[parent] all children have exited.\n";
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NOTE: check your limit on open files (ulimit -n) to see how many children you can have.
Typical systems may have a limit of only 1024, but this might be tweakable.