use strict;
use Data::Dumper;

my @a = (1, 2 ,3 , "a");
my %h;

a2h (\@a, \%h);

print Dumper (\%h);

print $h{1}{2}{3}{a};

sub a2h
{
    my $array = shift;
    my $hash  = shift;
    my $index = 0;

    while ( $index < $#$array )
    {
        $hash = $hash->{$array->[$index]} = {};
        $index++;
    }

    $hash->{$array->[$index]} = 1;

    return $hash;
}

#Output:
#
#$VAR1 = {
#          '1' => {
#                   '2' => {
#                            '3' => {
#                                     'a' => 1
#                                   }
#                          }
#                 }
#        };
#1
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