my %kid;
for (@kids) {
    my $cpid = fork;
    defined $cpid or warn("Couldn't fork"), next;
    $cpid or do {    # child
        close $in or die $!;
        select $out;
        $| = 1;
        $_->();
        exit 0;
    };
    $kid{$cpid} = undef;
}