use Data::Dumper;

my @fields = split /;/, $s;
my @array;
my $i = 0;
for my $x (0..2) {
    for my $y (0..2) {
        for my $z (0..2) {
            $array[$x]->[$y]->[$z] = $fields[$i];
            $i++;
        }
    }
}
print Dumper \@array;