Perl5 リファレンス

       split /PATTERN/,EXPR,LIMIT

       split /PATTERN/,EXPR

       split /PATTERN/

       split   Splits a string into a list of strings and returns
               that list.  By default, empty leading fields are
               preserved, and empty trailing ones are deleted.

               If not in list context, returns the number of
               fields found and splits into the `@_' array.  (In
               list context, you can force the split into `@_' by
               using `??' as the pattern delimiters, but it still
               returns the list value.)  The use of implicit
               split to `@_' is deprecated, however, because it
               clobbers your subroutine arguments.

               If EXPR is omitted, splits the `$_' string.  If
               PATTERN is also omitted, splits on whitespace
               (after skipping any leading whitespace).  Anything
               matching PATTERN is taken to be a delimiter
               separating the fields.  (Note that the delimiter
               may be longer than one character.)

               If LIMIT is specified and positive, splits into no
               more than that many fields (though it may split
               into fewer).  If LIMIT is unspecified or zero,
               trailing null fields are stripped (which potential
               users of `pop' would do well to remember).  If
               LIMIT is negative, it is treated as if an
               arbitrarily large LIMIT had been specified.

               A pattern matching the null string (not to be
               confused with a null pattern `//', which is just
               one member of the set of patterns matching a null
               string) will split the value of EXPR into separate
               characters at each point it matches that way.  For

                   print join(':', split(/ */, 'hi there'));

               produces the output 'h:i:t:h:e:r:e'.

               The LIMIT parameter can be used to split a line

                   ($login, $passwd, $remainder) = split(/:/, $_, 3);

               When assigning to a list, if LIMIT is omitted,
               Perl supplies a LIMIT one larger than the number
               of variables in the list, to avoid unnecessary
               work.  For the list above LIMIT would have been 4
               by default.  In time critical applications it
               behooves you not to split into more fields than
               you really need.

               If the PATTERN contains parentheses, additional
               list elements are created from each matching
               substring in the delimiter.

                   split(/([,-])/, "1-10,20", 3);

               produces the list value

                   (1, '-', 10, ',', 20)

               If you had the entire header of a normal Unix
               email message in $header, you could split it up
               into fields and their values this way:

                   $header =~ s/\n\s+/ /g;  # fix continuation lines
                   %hdrs   =  (UNIX_FROM => split /^(\S*?):\s*/m, $header);

               The pattern `/PATTERN/' may be replaced with an
               expression to specify patterns that vary at
               runtime.  (To do runtime compilation only once,
               use `/$variable/o'.)

               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.


                   open(PASSWD, '/etc/passwd');
                   while () {
                       ($login, $passwd, $uid, $gid,
                        $gcos, $home, $shell) = split(/:/);

               (Note that $shell above will still have a newline
               on it.  See the chop, chomp, and join entries
               elsewhere in this document.)