wait/waitpid returns -1 when there are no children or the children are automatically being reaped ( according to perldoc -f wait ). So the loop is waiting for all of the children to exit

I personally don't like this child count decrementing business... I'd rather explicitly check if the pid that I just got is the pid that I'm waiting for, i.e., my child. That may just be me...

 ## XXX - I use hashes in this type of situation 
 ## because I usually associate more meta data to a pid
 ## which must be used by the parent when the child
 ## exits... and delete $hash{ $foo } is cleaner
 ## than splice() to me :)

 use POSIX;
 my %pids;
 for( 1 .. $numchild ) {
    my $pid = fork();
    ## check if $pid id defined, etc.
    if( $pid ) { ## parent
       $pids{ $pid } = 1;
    } else {
       do_interesting_stuff();
       exit;
    }
 }

 while( ( my $pid = waitpid(-1, POSIX::WNOHANG() ) ) > 0 ){
    if( exists $pids{ $pid } ) {
        delete $pids{ $pid };
    } else {
        print STDERR "Unknown child $pid\n";
    }
 }
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