use PerlIO::via::MD5;
use Digest::MD5 qw(md5_hex);
use Benchmark qw(:all);

my $file = "data.txt";

cmpthese(-5, {
   perlio  => \&perlio,
   regular => \&regular,   
});

sub perlio {
   local($/) = undef;
   open(FILE,"<:via(MD5)", $file);
   my $digest = <FILE>;
   close FILE;
}

sub regular {
   local($/) = undef;
   open FILE, "<$file";
   my $data = <FILE>;
   close FILE;

   md5_hex($data);
}