you can easily modify the above code to have something like:

use strict;
use warnings;
use Data::Dumper;
my @AoH ;
my $current_hash = {};
while (<DATA>){
    chomp $_;
    if ( $_ =~ /objet => debut$/ .. /objet => fin$/){
        if ( /objet => debut$/ ){
            next;
        }
        elsif ( /objet => fin$/ ){
            push @AoH, $current_hash;
            $current_hash = {};
        }
        else{
            my ($key,$value) = split /\s+=>\s+/,$_;
            $current_hash->{ $key } = $value;
        }
    }
    else{
        print "unxpected content outside tags in line: [$_]\n";
    }
}
print Dumper \@AoH;
__DATA__
objet => debut
index => 1
a => "premiere valeur"
z => "dernier mot"
objet => fin
ALIEN LINE AFTER fin
objet => debut
index => 77
a => "autre valeur"
z => "aurai-je le dernier mot ?"
objet => fin
[download]

The above code use $current_hash as temporary container for key values pairs and need to be reset when fin is encountered. It outputs:

unxpected content outside tags in line: [ALIEN LINE AFTER fin]
$VAR1 = [
          {
            'a' => '"premiere valeur"',
            'index' => '1',
            'z' => '"dernier mot"'
          },
          {
            'z' => '"aurai-je le dernier mot ?"',
            'a' => '"autre valeur"',
            'index' => '77'
          }
        ];
[download]

L*