Hello Nansh,

Another not best way I would say, but I wanted to give it a try. :D

#!usr/bin/perl
use strict;
use warnings;
use Data::Dumper qw(Dumper);

my %hash;
my %cars;

while(<>) {
    chomp;
    next if /^\s*#/;  # skip comments
    next unless length; # skip white lines

    if ($_ =~ /^CARS/) {
    my @car_list = split ' ', $_;
    shift @car_list; # or splice @car_list, 0, 1;
        $cars{shift @car_list} = \@car_list;
    } elsif ($_ !~ /^CARS/) {
        my @keys = keys %cars;
        my @values = values %cars;
    $hash{$_}{$keys[0]} = shift @values;
    delete $cars{shift @keys};
    }
} continue {
    close ARGV if eof;  # Not eof()!
}

print Dumper \%hash;

__DATA__

CARS TOYOTO Etios Innova Camry Fortuner Corolla

*.This is Class cars.

CARS HYUNDAI Verna i10 i20 Eon Xcent Tucson

*.It is best cars.

CARS HONDA City Brio Amaze Accord

*.This is Luxury cars.

__OUTPUT__

$ perl test.pl input.txt
$VAR1 = {
          '*.This is Luxury cars.' => {
                                        'HONDA' => [
                                                     'City',
                                                     'Brio',
                                                     'Amaze',
                                                     'Accord'
                                                   ]
                                      },
          '*.This is Class cars.' => {
                                       'TOYOTO' => [
                                                     'Etios',
                                                     'Innova',
                                                     'Camry',
                                                     'Fortuner',
                                                     'Corolla'
                                                   ]
                                     },
          '*.It is best cars.' => {
                                    'HYUNDAI' => [
                                                   'Verna',
                                                   'i10',
                                                   'i20',
                                                   'Eon',
                                                   'Xcent',
                                                   'Tucson'
                                                 ]
                                  }
        };
[download]

Update: Removing two unnecessary lines (code untested)

Update2: Correcting buggy code.