#!/usr/bin/perl -w
use strict;
use Data::Dumper;

my @bigArray = qw(brown red+green blue+yellow black red+white purple+orange+gray);
my %hash;

for (@bigArray) {
    my @keys = split /\+/;
    my $ptr = \%hash;
    $ptr = $ptr->{$_} ||= {} for @keys[0..$#keys-1]; # work done here
    $ptr->{$keys[-1]} = 1;
}

print Dumper(\%hash);
__END__

##</code><code>##

$VAR1 = {
          'blue' => {
                      'yellow' => 1
                    },
          'purple' => {
                        'orange' => {
                                      'gray' => 1
                                    }
                      },
          'brown' => 1,
          'black' => 1,
          'red' => {
                     'green' => 1,
                     'white' => 1
                   }
        };