[Mailmunge] Add Header based on condition in filter_recipient{}

[list at ptld.com]

> You can just use Storable to dump/restore data to/from a file in the current directory.
> I don't think that needs a wrapper; it's already very simple.

You're right, im convinced this would be better than SQL. Thanks.

Last question on this, is there something in mailmunge / $ctx that tells me which filter im working from?
So my subs know if they were called from filter_recipient() vs filter_message()?
Or do i need to pass/global my own indicator to the subs?