pl@nereida:~/src/perl/perltesting$ cat ./timeregexpwithp.pl
#!/usr/local/lib/perl/5.10.1/bin//perl5.10.1 -w
use strict;
use Benchmark qw{:all};

cmpthese(
  1000000,
  {
    p => q{'hola juan' =~ /ju/p; my ($a, $b, $c) = (${^PREMATCH}, ${^MATCH}, ${^POSTMATCH} ) },
    oldway => q{'hola juan' =~ /ju/; my ($a, $b, $c) = ($`, $&, $') }
  }
);

cmpthese(
  10000000,
  {
    pnoassign => q{'hola juan' =~ /ju/p; },
    oldwaynoassign => q{'hola juan' =~ /ju/; }
  }
);

##</code><code>##

pl@nereida:~/src/perl/perltesting$ ./timeregexpwithp.pl
           Rate      p oldway
p      892857/s     --    -6%
oldway 952381/s     7%     --
                    Rate oldwaynoassign      pnoassign
oldwaynoassign 3184713/s             --            -1%
pnoassign      3225806/s             1%             --