use Time::HiRes qw/time/;

my $start = time;
my %save;
for(0 .. 2000000) {
    $save{$_}{$_+1}=$_+2;
}
print "hash: ", time - $start, "\n";

$start = time;
my @save;
for(0 .. 2000000) {
    $save[$_]{$_+1}=$_+2;
}
print "array: ", time - $start, "\n";

#Ouput:
#hash: 4.92373299598694
#array: 3.34077191352844