I had written,
| > Walter Dnes had a bunch of conditions beginning like this:
| >
| > * ^^.*$+rest_of_regexp
... which I misread as ^^(.*$)+ when I was responding before... sigh.
| > ... and the regexp was one that couldn't match on the
| > first line
and Walter asked me,
| Are there any instances where a message wouldn't begin
| with something like "From foo(_at_)bar" in the first line? If
| so, your concern would be valid. My filters are intended
| for use with sendmail and/or Exim if it makes any difference.
Well, whatever you have in "rest_of_regexp" won't match if it occurs only in
the top line, because you're expecting at least one newline before it, and
with "^^" there, "$" won't be able to match the opening putative newline.
If the expression were
.*$+rest_of_regexp
without ^^, then .* could match nothing, $+ could match the opening putative
newline, and rest_of_regexp could match the very first real contents of the
search area.