use PerlIO::via::MD5;
     use Digest::MD5 qw(md5_hex);
     use Benchmark qw(:all);
 
     my $file = "somebigfile.dat";
 
     timethese(-1, {
         perlio  => \&perlio,
         regular => \&regular,
     });
 
     sub perlio {
         open(my $in,"<:via(MD5)", $file)
             or die "Can't open file for digesting: $!\n";
         my $digest = <$in>;
         close $in;
         return $digest;
     }
 
     sub regular {
         local($/) = undef;
         open FILE, $file
             or die "Can't open file for digesting: $!\n";
         my $data = <FILE>;
         close FILE;
 
         return md5_hex($data);
     }