How do I change which characters OS X considers ‘a word’, for ⌥-arrow-key skipping? When I type ⌥→, I'd like my cursor to stop at periods, and perhaps other characters.

Does anybody know of a defaults configuration, or System Preferences setting, that changes which characters are considered to be ‘word characters’ by OS X?
The Word Break option has been removed in Mavericks.
Instead:

defaults write .GlobalPreferences AppleTextBreakLocale en_US_POSIX


Sources: https://twitter.com/jaydisc/status/393157866812502016 and http://lri.me/osx.txt