I'm using Blue_cowdawg's code. It does this:

$SIG{CHLD}=\&catchChildDeath;

#  Deal with the death of a child.  A sad event to be sure. 
sub catchChildDeath{
    printf "Death of child noted.\n";
    $children--;
    $children = ( $children < 0 ? 0 : $children);
    unless ($spawnEnabled){
        $spawnEnabled = ( $children < $min_child ? 1 : 0 );
    }
    printf "There are %d children running\n",$children;

}
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My sub that the child runs exits at its end:

sub my_child_work{
                my $x = shift;
                print "child x $x ";
                sleep 1;
                exit;
}
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