#!/usr/bin/env perl

use strict;
use warnings;

use Data::Dumper;

my $jid = '777';
my $text = 'header 777 111 777 A 222 777R-1 333 777R-2 A 444';
my $re = qr{(?x: \A (R-\d+|) \s*? (A|) \s (\d+) )};
my @lines;
my $wanted_line = 0;

for my $line (split /$jid/, $text) {
    next unless $wanted_line++;
    my @fields = $line =~ $re;
    push @lines, [ $jid . shift(@fields), @fields ];
}

print Dumper(\@lines);

##</code><code>##

$VAR1 = [
          [
            '777',
            '',
            '111'
          ],
          [
            '777',
            'A',
            '222'
          ],
          [
            '777R-1',
            '',
            '333'
          ],
          [
            '777R-2',
            'A',
            '444'
          ]
        ];

##</code><code>##

$ perl -e 'my @x = qw{a b c d e f}; print join ",", @x[0,3,4]'
a,d,e