alt+left or alt+right doesn't work for me in Terminal out of the box (I usually use iTerm2 where it doesn't work either) - do you need to change any settings (such as emulation, terminal type etc) to get at that?
According to this[1] stack overflow post, the vim key bindings for move back and forward work by default (which is news to me), or you can set up the alt left and right behaviour by following the instructions here[2].