As a special case, specifying a PATTERN of space
  ("' '") will split on white space just as "split"
  with no arguments does.  Thus, "split(' ')" can be
  used to emulate awk's default behavior, whereas
  "split(/ /)" will give you as many null initial
  fields as there are leading spaces.  A "split" on
  "/\s+/" is like a "split(' ')" except that any
  leading whitespace produces a null first field.  A
  "split" with no arguments really does a 
  "split(' ', $_)" internally.