output.txt

ok 1 - unpack works
ok 2 - substr works
ok 3 - regex works
1..3
           Rate  regex unpack substr
regex  298898/s     --   -45%   -67%
unpack 541032/s    81%     --   -40%
substr 899326/s   201%    66%     --

string-extract-benchmark.pl

#!/usr/bin/perl                                                                                                               
                                                                                                                             
use strict;                                                                                                                   
use warnings;                                                                                                                 

use Benchmark qw(cmpthese);
use Test::More;            

my $data = "100020003000.png";

sub using_unpack {
  my ($dir, $name, $file, $ext) = unpack "A4A4A4xA3", $data;
  return ($dir, $name, $file, $ext);
}

sub using_substr {
  my $dir = substr $data, 0, 4;
  my $name = substr $data, 4, 4;
  my $file = substr $data, 8, 4;
  my $ext = substr $data, 13, 3;
  return ($dir, $name, $file, $ext);
}

sub using_regex {
  my ($dir, $name, $file, $ext) = $data =~ /^(.{4})(.{4})(.{4})\.(.{3})$/;
  return ($dir, $name, $file, $ext);
}

is_deeply [ using_unpack() ], [1000, 2000, 3000, "png"], "unpack works";
is_deeply [ using_substr() ], [1000, 2000, 3000, "png"], "substr works";
is_deeply [ using_regex() ], [1000, 2000, 3000, "png"], "regex works";
done_testing;

cmpthese( -3, {
    unpack => \&using_unpack,
    substr => \&using_substr,
    regex => \&using_regex,
  },
);