child_cb.pm

package fork::child_cb;

use strict;

my @CHILD_CB;

BEGIN {
    *CORE::GLOBAL::fork = sub() {
        my $ret = CORE::fork;
        if ( defined($ret) && $ret == 0 ) {
            $_->() for @CHILD_CB;
        }
        return $ret;
    };
}

sub add(&) {
    push @CHILD_CB, $_[0];
    1;
}
1;