use Benchmark qw/countit cmpthese/;
sub run($) { countit(5, @_) }
for $size (2, 200, 20_000) {
    $s = "." x $len;
    print "\nDATASIZE = $size\n";
    cmpthese {
        chop2   => run q{
            $t = $s; chop $t; chop $t;
        },
        subs    => run q{
            ($t = $s) =~ s/..\Z//s;
        },
        lsubstr => run q{
             $t = $s; substr($t, -2) = '';
        },
        rsubstr => run q{
             $t = substr($s, 0, length($s)-2);
        },

    };
}