There are many ways, some are ugly, and none especially perl.

have your webserver run as root, you can then make the files whatever you want ;-)
 This is of course, a Bad Idea.

clever use of the Group directive

http://stein.cshl.org/WWW/software/sbox/

http://cgiwrap.sourceforge.net/

http://www.snert.com/Software/mod_become/index.shtml

UPDATE: I forgot to mention (memory spurred by tangential remark by jeffa), setting the directory to setgid. Thus if nobody and user are in a group, and the directory is group writable and setgid group all files created within will be in the group and editable by both. I have done this before, it can get a little hairy though. This works best with a RedHat type system, since each user has their own group. All that is required is to add nobody to each of these groups.

Achh, I can't believe I missed suexec! Zaxo++. (Suexec can be a major pain though, most notably the DocumentRoot gets locked in at compile time) I actually used both suexec and the setgid trick together. The reason why I needed the setgid supplement is that I was also using mod_dav. With WebDAV files are created by the webserver *proper*...

PS> umask 002 could not give you a file that is a+w (or even o+w to be more specific).

--
perl -pe "s/\b;([st])/'\1/mg"