Somewhere amid the MIME-encoding in Martin Ramsch's post, he asked Philip
Guenther, who had suggested,
| >     * ARG ?? ^^some-value^^
this question:
| Still being rather new to procmail I wonder why you don't use the more
| familiar "^" and "$" anchors:
| 
|   * ARG ?? ^some-value$
| 
| Are there situations where the "^^" anchors do work better for one
| line matches?
When the search area contains more than one line, yes.  ^ and $ might match
any newline in the search area.  ^^ and ^^ anchor only at the very beginning
and the very end.