use strict;

use Data::Dumper;

$_ = "10001 LONG RECORD\n
BEGIN RECORD A, CODE B, TABLE C END \n
NEXT\n
STANDARD DATA 1 BEGIN CODE A, RECORD B END NEXT\n
SHORT RECORD BEGIN TABLE B END NEXT\n
STANDARD DATA 2 BEGIN CODE C, RECORD D, FILE END;";

my(@records) = m< \bBEGIN\b \s+ (.*?) \s+ \bEND\b >gx;

print Dumper(\@records);

__output__

$VAR1 = [
          'RECORD A, CODE B, TABLE C',
          'CODE A, RECORD B',
          'TABLE B',
          'CODE C, RECORD D, FILE'
        ];

##</code><code>##


my @subrecs;
for(@records) {
  my @items = split ', ';
  push @subrecs => [
    [map { (split ' ')[0] } @items],
    [map { (split ' ')[1] } @items],
  ];
}

print Dumper(\@subrecs);


__output__

$VAR1 = [
          [
            [
              'RECORD',
              'CODE',
              'TABLE'
            ],
            [
              'A',
              'B',
              'C'
            ]
          ],
          [
            [
              'CODE',
              'RECORD'
            ],
            [
              'A',
              'B'
            ]
          ],
          [
            [
              'TABLE'
            ],
            [
              'B'
            ]
          ],
          [
            [
              'CODE',
              'RECORD',
              'FILE'
            ],
            [
              'C',
              'D'
            ]
          ]
        ];