use Benchmark 'cmpthese';
use Regexp::Keep;
my $s = "abc.def.ghi.jkl";
cmpthese(-5, {
  japhy => sub { (my $x = $s) =~ s/.*\K\..*// },
  old   => sub { (my $x = $s) =~ s/(.*)\..*/$1/ },
});

##</code><code>##

old   = 40280.54/s
japhy = 74338.79/s

##</code><code>##

old   =  58188.18/s
japhy = 102409.25/s