If you're seeing an error similar to:
(?:(?<=[\s,]))* matches null string many times in regex; marked by <-- HERE in m/\G(?:(?<=[\s,]))* <-- HERE \Z/ at /opt/local/lib/perl5/5.8.7/Text/Wrap.pm line 46.
This issue is popping up more and more on the users list and in irc. The short version is that newer versions of Text::Wrap (not associated with SpamAssassin) throw this warning for a regular expression that has been in use for years. It's been reported as a bug to the Text::Wrap authors already.
3.1.8 and 3.2 and beyond have a work-around to avoid displaying the warning from Text::Wrap. Alternately, you can downgrade your installation of Text::Wrap to an earlier version which doesn't have this issue.
This issue was originally reported in SpamAssassin Bugzilla ticket 5056:
http://issues.apache.org/SpamAssassin/show_bug.cgi?id=5056
For a discussion about downgrading Text::Wrap, please see the following thread:
http://www.mail-archive.com/users@spamassassin.apache.org/msg34628.html