Despite much effort, I have not found a built-in or plugin-assisted way to do what you're trying to do. I completely agree that it should be possible, as the program can distinguish foo
from buffoon
when you first highlight it, but no one seems to know a way of doing it.
However, here are some useful key combos for selecting words in Sublime Text 2:
Ctrl?G - selects all occurrences of the current word (AltF3 on Windows/Linux)
?D - selects the next instance of the current word (CtrlD)
?E, ?H - uses the current selection as the "Find" field in Find and Replace (CtrlE,CtrlH)