Rate    bt_c    mult      bt     opt     mod    chop
bt_c    180870/s      --     -1%     -5%    -28%    -62%    -74%
mult    181987/s      1%      --     -4%    -27%    -62%    -74%
bt      189426/s      5%      4%      --    -24%    -60%    -73%
opt     249612/s     38%     37%     32%      --    -48%    -64%
mod     476214/s    163%    162%    151%     91%      --    -31%
chop    692944/s    283%    281%    266%    178%     46%      --

##</code><code>##

use Benchmark 'cmpthese';

$x = int (1_000_000 * rand 1_000_000);

cmpthese( -3, {
  mult => sub { $x =~ /(\d)*(\d)/  },
  bt_c => sub { $x =~ /(\d*)(\d)/  },
  bt   => sub { $x =~ /\d*(\d)/    },
  opt  => sub { $x =~ /(\d)$/      },
  mod  => sub { $x % 10            },
  chop => sub { my $x= $x; chop $x },
});

##</code><code>##

        Rate    mult   bt_c     bt    opt    mod     chop
mult 180759/s     --    -1%    -7%   -31%   -62%     -71%
bt_c 182581/s     1%     --    -6%   -31%   -62%     -70%
bt   193680/s     7%     6%     --   -26%   -60%     -69%
opt  263234/s    46%    44%    36%     --   -45%     -57%
mod  481067/s   166%   163%   148%    83%     --     -22%
chop 618559/s   242%   239%   219%   135%    29%       --

##</code><code>##

use Benchmark 'cmpthese';

$x = int (1_000_000 * rand 1_000_000);

cmpthese( -3, {
  mult => sub { $x =~ /(\d)*(\d)/ },
  bt_c => sub { $x =~ /(\d*)(\d)/ },
  bt   => sub { $x =~ /\d*(\d)/   },
  opt  => sub { $x =~ /(\d)$/     },
  mod  => sub { $x % 10           },
  chop => sub { local $x; chop $x },
});