Stephane Chazelas wrote:
> one can
> use (?m) if he wants ^ to match the beginning of each line in
> the NUL-delimited record instead of just the beginning of the
> record.

I think the intent is that ^ and $ should match only the line-terminator 
specified by -z (or by -z's absence). So the sort of usage you describe is 
unspecified and not supported. That being said, it does make sense to match 
tricky regular expressions like that line by line, even if this hurts 
performance. Otherwise, I suspect there are even trickier regular expressions 
that could reject a buffer full of lines even though it contains matching lines. 
When in doubt we should avoid optimization so I installed the attached patch 
into the master branch. Please give it a try.