use strict;
use warnings;
use Benchmark 'cmpthese';

cmpthese -2, {
    1 => sub { 
        my ( $s, $x, $y ) = 0;
#        for ( 1 .. 1e6 ) {         # doesn't matter, if written so
        for my $i ( 1 .. 1e6 ) {
            $x = rand;              # suppose intermediate 
            $y = rand;              # variables are required
            $s += $x + $y;
        }
        $s
    },
    2 => sub { 
        my ( $s, $i ) = 0;
#        for $i ( 1 .. 1e6 ) {      # doesn't matter, neither
        for ( 1 .. 1e6 ) {
            my $x = rand; 
            my $y = rand;
            $s += $x + $y;
        }
        $s
    },
};

__END__

    Rate    2    1
2 6.69/s   -- -42%
1 11.6/s  74%   --