package MyPairList;
use strict;
use warnings;
use feature 'state';
use Data::Dumper;
use List::Util qw(all none);
use Exporter 'import';
our @EXPORT = qw(pair_list_parse);

sub pair_list_parse {
my $string = shift;
sub get_tokens {
    my $string = shift;
    my @tokens = $string =~ /([()]|[^()\s]+)/g;
}
my @tokens = get_tokens $string;

sub parse_list {
    state @tokens = @_;
    my @list;
    while (my $token = shift @tokens) {
        if ($token eq '(') {
            push @list, parse_list();
        } elsif ($token eq ')') {
            return \@list;
        } else {
            push @list, $token;
        }
    }
    return \@list;
}

my $list = parse_list @tokens;

sub parse_nested_list {
    my ($list) = @_;
    my %hash;
    if (none {ref $_} @$list) {
      if (@$list == 1) {
        return $list->[0];
      } elsif (@$list == 2) {
        return { $list->[0] => $list->[1] };
      } else {
        return $list
      }
    } elsif (all {ref $_} @$list) {
        return [ map { parse_nested_list($_) } @$list ];
    } else {
        my ($key, $ref, @remain) = @$list;
        die 'wrong key ', Dumper $key if ref $key;
        die 'wrong value ', Dumper $ref unless ref $ref;
        die 'redundant value', Dumper \@remain if @remain;
        $hash{$key} = parse_nested_list($ref);
    }
    return \%hash;
}
return parse_nested_list($list)
}
1;

##</code><code>##

(config(
    (a A)
    (b B)
    ((good) (bad))
    (d e f)
    (a (a1 (a2 A)))
)
)

##</code><code>##

$VAR1 = [
          {
            'config' => [
                          {
                            'a' => 'A'
                          },
                          {
                            'b' => 'B'
                          },
                          [
                            'good',
                            'bad'
                          ],
                          [
                            'd',
                            'e',
                            'f'
                          ],
                          {
                            'a' => {
                                     'a1' => {
                                               'a2' => 'A'
                                             }
                                   }
                          }
                        ]
          }
        ];