Hook in external programs

Hi,

I'm new to maildrop and need some advice on how to set it up. I
don't do anything fancy, just a few filters to sort mail into
folders.

For important mails I'd like to have a notification. What is the
best way to hook in an external program like notify-send? Here is an
example of what I'd like to do:

if (/^List-ID: .*(alpha\.lists\.sourceforge\.net)/:h)
to "$MAILHOME/.Lists.alpha"
# notify-send 'New mail! List: alpha' 'From: **From**'

if (/^List-ID: .*(beta\.lists\.sourceforge\.net)/:h)
to "$MAILHOME/.Lists.beta"
# notify-send 'New mail! List: beta' 'From: **From**'

The external program notify-send should be invoked before or after
the mail is placed in the corresponding folder including information
about who sent the mail.

How do I hook notify-send into the filters?
How do I access the From: header to be provided as argument to
notify-send?

Best regards

Marco


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