use strict;
use warnings;
use Benchmark qw(cmpthese timethese);

my %subs;

###############################################################################

my $UPPER = 1_000_000;

$subs{vec} = sub {
    my $sieve = "";
    GUESS: for my $guess (2 .. $UPPER) {
        next GUESS if vec($sieve,$guess,1);
        #print "$guess\n";
        for (my $mults = $guess * $guess; $mults <= $UPPER; $mults += $guess) {
            vec($sieve,$mults,1) = 1;
        }
    }
};

$subs{substr} = sub {
    my $sieve = '0' x ($UPPER + 1);
    GUESS: for my $guess (2 .. $UPPER) {
        next GUESS if substr($sieve,$guess,1);
        #print "$guess\n";
        for (my $mults = $guess * $guess; $mults <= $UPPER; $mults += $guess) {
            substr($sieve,$mults,1,1);
        }
    }
};

###############################################################################

cmpthese(timethese(-60, \%subs));