use Benchmark qw/:all/;
use strict;
my $SQUARE;
my $MIN_NUMBER = 4;
my $MAX_NUMBER = 1000;
foreach my $number ($MIN_NUMBER..$MAX_NUMBER){
    my $square  = $number * $number;
    $SQUARE->{$square} = $number;
}
my $string = q(5973821902497150366459738219024971503664);

sub m_re {
    my $total_length;
    foreach my $square (keys %{$SQUARE}){
        if($string =~ /$square/) {
            my $length =  length($square);
            $total_length  += $length;
        }
    }
    return ($total_length);
}
sub m_index {
    my $total_length;
    foreach my $square (keys %{$SQUARE}){
        if(index($string, $square) > 0) {
            my $length =  length($square);
            $total_length  += $length;
        }
    }
    return ($total_length);
}

sub m_sqrt {
    my $total_length;
    my %seen;
    for my $start (0..length $string) {
        next if substr($string, $start, 1) eq '0';
        for my $length (1..(length($string)-$start)) {
            my $test = substr($string, $start, $length);
            my $sqrt = sqrt($test);
            if (!$seen{$test}++ and $sqrt == int $sqrt
                    and $sqrt >= $MIN_NUMBER and $sqrt <= $MAX_NUMBER) {
                $total_length += $length;
            }
        }
    }
    return ($total_length);
}

cmpthese(1000, {
    "Regexp", \&m_re,
    "Index", \&m_index,
    "Sqrt", \&m_sqrt,
});