JunkMatcher can be added to Mail.app as a rule so it can be used hand-in-hand with Mail.app's built-in (statistical) junk filter. Users can decide what actions to take on the matched messages (mark as junk/read/flagged/colored, move them to Junk/Trash mailbox etc.).
A self-contained GUI - JunkMatcher Central is also included so you can conduct "Email forensics": testing and building your regular expression patterns, browsing the log file of the past matchings, etc. You can even report spam to SpamCop.net directly from the log window. Many settings are also available in it so you can customize the entire matching process to your heart's content.