Synopsis:
   bind <key> backward_word

Description:
   This function moves the cursor backward until it reaches the beginning
   of a word.  If the cursor is currently in the middle of a word, it is
   shifted to the beginning of that word.  If it is already at the
   beginning of a word, or on whitespace of any kind, it is moved back to
   the previous word.  It has no effect if the cursor is at the beginning
   of the first word.

See Also:
   bind(4) forward_word