When I recently saw this output on my mac, I was shuffled back to the old days of Solaris 7 and FACLs:
2014-04-05 04:00:23 george2@g2mac:~
0$ ls -alF
-rw-r--r--@ 1 george2 staff 3569 Apr 5 15:47 test.py
-rw-r--r--@ 1 george2 staff 146 Apr 5 15:47 test.txt
It makes sense that Darwin has some sort of extended attributes, and we've been seeing it for years on mac, but I never tried to fuss with it on the command line. Every OS is getting in on this, but I haven't seen a consensus on what the 11th character should be (@, ., *), but if there's 11 characters for permissions, you can be sure there's something more going on.