my @keys = ('level1_1', 'level2_1', 'level3_1');

my %hash = ();
$hash{data} = {};

my $hashref = $hash{data};
for my $i (0..$#keys) {
        $hashref->{$keys[$i]} = ($i == $#keys ? 'test' : {});
        $hashref = $hashref->{$keys[$i]};
}



print "Dumper: '".Dumper(\%hash)."'<br>\n";