If you follow perl5-porters, you'll know this already, but I think this deserves all the exposure it can.
Long-time perl users might be aware that perl's regular expression engine is a recursive implementation. This usually work ok, except on rather pathological cases where so much recursion takes place that the C stack runs out of space and the process dies with a segmentation fault.
perl -le '$x = "o" x shift; $x =~ s/(o?)+//g' 10000
# Bus error: 10 (core dumped)
(if the above doesn't crash for you, just up the 10000 a bit).
Just last week, [dave_the_m] checked a patch into the perl source code repository that converts the algorithm used from recursive to iterative. Since then [steve_p] has been busily going through the bug database, closing out dozens of bugs that have been corrected due to this change. All in all it's a stunning piece of work, and Dave deserves to be congratulated for it.
The code is now in blead. Once it's settled a while, it may be backported to the maintenance track, and it will start to appear in the 5.8 series. Otherwise you'll have to wait until 5.10.
Read [http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00793.html|Dave's announcement].
• another intruder with the mooring in the heart of the Perl
-sam
Well, the announcement seems to imply that this is just the first iteration at getting a good iterative solution. ;-)
Hopefully the next iteration results in something a little less spaghetti-like, and maybe something more like rotini with all the appropriate spirals and ... mmmm, I think it's lunch time.