Filter emails in Mail.app with regular expressions

gistfile1.applescript

-- Mail.app can't run a "Contains" filter with a regex,
-- so you can't filter on HTML content. Until now.
using terms from application "Mail"
  on perform mail action with messages theMessages for rule theRule
		try
			repeat with theMessage in theMessages
				-- Getting the content as string converts all HTML tags to '?' and just leaves text content
				set theBody to quoted form of (theMessage's content as string)
				-- It's awkwardly hard to get sed to work w/ mult. lines, so collapse newlines
				set theCommandString to "echo " & theBody & " | tr '\\n' ' ' | sed \"s/brett Author/*MATCHED*(&)/\"" as string
				set sedResult to do shell script theCommandString
				if sedResult contains "*MATCHED*" then
					tell application "Mail"
						move the theMessage to mailbox "My special mailbox"
					end tell
				end if
			end repeat
		on error errorText number errorNumber
			tell application "Mail" to display alert ("Error: " & errorNumber) message errorText
			return
		end try
	end perform mail action with messages
end using terms from