As another special case, "split" emulates the default behavior of
            the command line tool awk when the PATTERN is either omitted or a
            string composed of a single space character (such as ' ' or
            "\x20", but not e.g. "/ /"). In this case, any leading whitespace
            in EXPR is removed before splitting occurs, and the PATTERN is
            instead treated as if it were "/\s+/"; in particular, this means
            that any contiguous whitespace (not just a single space character)
            is used as a separator. However, this special treatment can be
            avoided by specifying the pattern "/ /" instead of the string " ",
            thereby allowing only a single space character to be a separator.
            In earlier Perls this special case was restricted to the use of a
            plain " " as the pattern argument to split; in Perl 5.18.0 and
            later this special case is triggered by any expression which
            evaluates to the simple string " ".

            If omitted, PATTERN defaults to a single space, " ", triggering
            the previously described awk emulation.