Bug 6968: quote a $ within a character class (Bleadperl v5.19.2-257-gc30fc27 fixes a bug in perl which Mail/SpamAssassin/Plugin/FreeMail.pm relies)

git-svn-id: https://svn.apache.org/repos/asf/spamassassin/trunk@1514524 13f79535-47bb-0310-9956-ffa450edef68