Philip Guenther suggested to wotan(_at_)netcom(_dot_)com:
| The lonely '.' in your fourth example, or the '()' in what I show (kudos
| to David Tamkin for the idea) serve to protect the backslash from this
| strippage.
Don't hang the messenger, but unless the reward is for the act of delivery
don't declare a national holiday for the messenger either. The idea of
using an empty pair of parentheses to delimit leading or trailing whitespace
came from Stephen van den Berg. [Procmail will read trailing whitespace in
a regexp, but a visible delimiter helps the human rcfile maintainer know
what's going on.]