Well, for starters it will be easier if you do your work in the children, and keep track of them using the parent.

Here's a bit of untested code that should probably do the trick...

#!/usr/bin/perl

use POSIX ":sys_wait_h";

$MAX = 20; #max num of children at a given time
$SIG{CHLD} = \&REAPER; #deal with our children

@list = (1,2,3); 
$count = 0; #number of children outstanding
foreach $item ($list) {
 while($count >= $MAX) { #too many children, wait awhile
  sleep(1);
 }

 if(fork) { #Parent
  $count++;
  next;
 }
 else { #Child
  print("$item\n"); #do some child stuff here
  exit;
 }
}

sub REAPER {
 my $pid;
 while($pid = waitpid(-1,&WNOHANG)) { 
  last if($pid == -1);
  $count--; #Decrement our outstanding children
 }
 \&REAPER; #Reinstall the signal hanler
}
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cephas