(chart ((1 ((title title-1) (xlable X-lab) (ylable Y-lab) (description desc1) (type line) (series ((1 ((x-data (1 2 3 4 5)) (y-data (20 90 60 50 30))))))))))

##</code><code>##

[
  "chart",
  [
    [
      1,
      [
        ["title", "title-1"],
        ["xlable", "X-lab"],
        ["ylable", "Y-lab"],
        ["description", "desc1"],
        ["type", "line"],
        [
          "series",
          [
            [
              1,
              [["x-data", [1, 2, 3, 4, 5]], ["y-data", [20, 90, 60, 50, 30]]],
            ],
          ],
        ],
      ],
    ],
  ],
]

##</code><code>##

{
  chart => {
        description => "desc1",
        series      => { "x-data" => [1, 2, 3, 4, 5], 
                         "y-data" => [20, 90, 60, 50, 30] },
        title       => "title-1",
        type        => "line",
        xlable      => "X-lab",
        ylable      => "Y-lab",
      },
}

##</code><code>##

use Data::Dump qw(dump);
print "x_data: ", dump($keyed_list->{chart}->{series}->{"x-data"}), "\n";
print "y_data: ", dump($keyed_list->{chart}->{series}->{"y-data"}), "\n";

# which outputs
#x_data: [1, 2, 3, 4, 5]
#y_data: [20, 90, 60, 50, 30]

##</code><code>##

package Data::SExpression::Special;

use Data::SExpression;
our @ISA = qw(Data::SExpression);

sub new_symbol { 
    shift;
    return shift;
}

package main;

use File::Slurp qw(read_file);

my $file = shift;

my $ds = Data::SExpression::Special->new();
my $sexp = $ds->read(read_file($file));

use Data::Dump qw(dump);
print dump($sexp);

# outputs this mess:
#[
#  "chart",
#  [
#    [
#      1,
#      [
#        ["title", "title-1"],
#        ["xlable", "X-lab"],
#        ["ylable", "Y-lab"],
#        ["description", "desc1"],
#        ["type", "line"],
#        [
#          "series",
#          [
#            [
#              1,
#              [["x-data", [1, 2, 3, 4, 5]], ["y-data", [20, 90, 60, 50, 30]]],
#            ],
#          ],
#        ],
#      ],
#    ],
#  ],
#]

# converts [ *a => $v ] to ( *a => to_keyed_list($v) )
sub to_keyed_pair {
    my $sexp = shift;
    my $k = $sexp->[0];
    my $v = $sexp->[1];
    my $val;
    if (ref $v eq 'ARRAY' &&
        ref $v->[0] eq 'ARRAY' &&
        $v->[0]->[0] eq '1' &&
        ref $v->[0]->[1] eq 'ARRAY') { # if is something like [ [ 1, [ @list_of_pairs ] ] ]
        $val = to_keyed_list($v->[0]->[1]);
    } else {
        $val = $v;
    }
    return ($k, $val);
}

sub to_keyed_list {
    my $list = shift;
    my %hash;
    for (@$list) {
        my ($k, $v) = to_keyed_pair($_);
        $hash{$k} = $v;
    }
    return \%hash;
}

my $keyed_list = to_keyed_list([ $sexp ]);
print dump($keyed_list);

# now that is a easy-to-access data structure
#{
#  chart => {
#        description => "desc1",
#        series      => { "x-data" => [1, 2, 3, 4, 5], 
#                         "y-data" => [20, 90, 60, 50, 30] },
#        title       => "title-1",
#        type        => "line",
#        xlable      => "X-lab",
#        ylable      => "Y-lab",
#      },
#}

#Now i want to get the value of x_data (1 2 3 4 5) and y_data (20 90 60 50 30)

print "x_data: ", dump($keyed_list->{chart}->{series}->{"x-data"}), "\n";
print "y_data: ", dump($keyed_list->{chart}->{series}->{"y-data"}), "\n";

# and then you got
#x_data: [1, 2, 3, 4, 5]
#y_data: [20, 90, 60, 50, 30]