`echo <something> | pfctl -mf -` overriding instead of modifying

[Dewayne Geraghty]

Niklaus,
Would you please reverse the order and advise?  That is try:
     exec.poststart += "echo 'rdr pass on vtnet0 inet6 proto { udp tcp } to
vtnet0 port domain ->   $private_ip6' | pfctl -a 'jails/$name' -mf -";
   exec.poststart += "echo 'rdr pass on vtnet0 inet  proto { udp tcp } to
vtnet0 port domain ->   $private_ip4' | pfctl -a 'jails/$name' -f -";

Regards, Dewayne.