use strict;
use warnings;
use Data::Dumper::Concise;
 
my $string = "aacbbbcac";
 
my $re = '((a+)?(b+)?(c))*';

# transform '(x+)?' to '(x*)' assuming 'x' is monolithic
$re =~ s/\Q+)?/*)/g;
print "re = $re\n";

my $re1 = qr/$re/;


if ($string =~ $re1) {
  my @something;
  foreach (0..$#-) {
    if(defined($-[$_])) {
        my $substring = substr($string, $-[$_], $+[$_] - $-[$_]);

        # ${$_} also works, except where $_ = 0
        no strict 'refs';
        print "\$substring = $substring = ${$_}\n";

        # transform '' to undef
        $substring = undef if($substring eq '');

        # assert: $substring is now as specified by
        # Standard ECMA-262, 5.1 Edition / June 2011
        # Section 15.10.2.5 Note 3

        printf "Group %d: <%s>\n", $_, $substring // '';
        $something[$_] = $substring;
    }
  }

  print Dumper(\@something);
}

##</code><code>##

re = ((a*)(b*)(c))*
$substring = aacbbbcac = test.pl
Group 0: <aacbbbcac>
$substring = ac = ac
Group 1: <ac>
$substring = a = a
Group 2: <a>
$substring =  =
Group 3: <>
$substring = c = c
Group 4: <c>
[
  "aacbbbcac",
  "ac",
  "a",
  undef,
  "c"
]