Sergey Yurzin


Sort::Naturally::XS - Perl extension for human-friendly ("natural") sort order


  use Sort::Naturally::XS;

  my @mixed_list = qw/test21 test20 test10 test11 test2 test1/;

  my @result = nsort(@mixed_list); # @result is: test1 test2 test10 test11 test20 test21

  @result = sort ncmp @mixed_list; # same, but use standard sort function

  @result = sort {ncmp($a, $b)} @mixed_list; # same as ncmp, but argument pass explicitly


Natural sort order is an ordering of mixed strings (consist of characters and digits) in alphabetical order, except that digital parts are ordered as numbers. Natural sorting can be considered as a replacement of a standard machine-oriented alphabetical sorting, because it is more convenient for human understanding. For example, the following list:

  test21 test20 test10 test11 test2 test1

after performing a standard machine-oriented alphabetical sorting, will be as follows:

  test1 test10 test11 test2 test20 test21

The sequence appears unnatural, because test10 and test11 come before test2. On the other hand, natural sorting gives a human-friendly sequence:

  test1 test2 test10 test11 test20 test21

now test2 comes before test10 and test11.



Replacement of the cmp standard operator. LEFT and RIGHT variables are presented for comparison. Returns 1 if LEFT should come before RIGHT, -1 if RIGHT should come before LEFT and 0 if LEFT and RIGHT match.

  # sort @list naturally, support in latest perl versions
  my @result = sort ncmp @list;

  # same, but arguments pass explicitly
  @result = sort {ncmp($a, $b)} @list;

  # more complex example, sort ARRAY of HASH refs by key 'foo' in descending order
  @result = sort {ncmp($b->{foo}, $a->{foo})} @list;

In list context returns a LIST sorted copy.

  my @result = nsort(@list);

Returns an ARRAY ref to a sorted list. First argument is an ARRAY ref to the source list, followed by keyword arguments, such as reverse and locale. If reverse is true the source list is sorted in reverse order. If locale is specified, the sorting will be performed according to the locale aware settings.

  use Sort::Naturally::XS qw/sorted/;

  my $result = sorted($list);

  $result = sorted($list, reverse => 1); # $list will be sorted in descending order

  # $list will be sorted according to en_US.utf8 locale
  $result = sorted($list, locale => 'en_US.utf8');


By default the sort function sorts according to a standard C locale or, if a use locale pragma is in effect, according to OS settings, which can be changed with the help of the setlocale function. The use of both use locale and setlocale has no effect on ncmp and nsort. The following example demonstrates this behavior:

  use POSIX;
  use Sort::Naturally::XS;

  my @list = ('a.'.'c', 'A'..'B');

  my @result_std = sort @list;
  my @result_ncmp = sort {ncmp($a, $b)} @list;
  # @result_std contains  A, B, C, a, b, c
  # @result_ncmp contains A, B, C, a, b, c

  use locale;
  # assumed that current locale is en_US.utf8
  @result_std = sort @list;
  @result_ncmp = sort {ncmp($a, $b)} @list;
  # @result_std contains  a, A, b, B, c, C
  # @result_ncmp contains A, B, C, a, b, c

  setlocale(POSIX::LC_ALL, 'en_CA.utf8');
  @result_std = sort @list;
  @result_ncmp = sort {ncmp($a, $b)} @list;
  # @result_std contains  A, a, B, b, C, c
  # @result_ncmp contains A, B, C, a, b, c

To be able to sort a list with an arbitrary locale it is necessary to use the sorted function with a locale keyword argument:

  use Sort::Naturally::XS qw/sorted/;

  my $list = ['a.'.'c', 'A'..'B'];

  my $result_us = sorted($list, locale => 'en_US.utf8');
  # $result_us contains a, A, b, B, c, C

  my $result_ca = sorted($list, locale => 'en_CA.utf8');
  # $result_ca contains A, a, B, b, C, c

Note: due to the complexity of a cross-platform support, a locale aware sorting is guaranteed on Unix-like operating systems only.


By default the module exports ncmp and nsort subroutines.


  require Benchmark;
  require Sort::Naturally::XS;
  require Sort::Naturally;

  my @list = (
      'H4', 'T25', 'H5', 'T27', 'H8', 'T30', 'HEX', 'T35', 'M10', 'T4', 'M12', 'T40', 'M13',
      'T45', 'M14', 'T47', 'M16', 'T5', 'M4', 'T50', 'M5', 'T55', 'M6', 'T6', 'M7', 'T60',
      'M8', 'T7', 'M9', 'T70', 'Ph0', 'T8', 'Ph1', 'T9', 'Ph2', 'TT10', 'Ph3', 'TT15', 'Ph4',
      'TT20', 'Pz0', 'TT25', 'Pz1', 'TT27', 'Pz2', 'TT30', 'Pz3', 'TT40', 'Pz4', 'TT45',
      'R10', 'TT50', 'R12', 'TT55', 'R13', 'TT6', 'R14', 'TT60', 'R5', 'TT7', 'R6', 'TT70',
      'R7', 'TT8', 'R8', 'TT9', 'S', 'TX', 'Sl', 'XZN', 'T10', 'T15', 'T20'

  Benchmark::cmpthese(-3, {
      my => sub { Sort::Naturally::XS::nsort(@list) },
      other => sub { Sort::Naturally::nsort(@list) },

  #          Rate other    my
  # other   561/s    --  -97%
  # my    20693/s 3588%    --

  Benchmark::cmpthese(-10, {
      std   => sub { sort @list },
      other => sub { sort {Sort::Naturally::ncmp($a, $b)} @list },
      my    => sub { sort {Sort::Naturally::XS::ncmp($a, $b)} @list },

  #            Rate other   std    my
  # other 7977106/s    --   -3%   -5%
  # std   8232321/s    3%    --   -2%
  # my    8426303/s    6%    2%    --


There are differences in sorting outcomes compared with the Sort::Naturally module. Capital letters always come before lower case letters, digits always come before letters.
  9x 14 foo fooa foolio Foolio foo12 foo12a Foo12a foo12z foo13a # Sort::Naturally
  9x 14 Foo12a Foolio foo foo12 foo12a foo12z foo13a fooa foolio # Sort::Naturally::XS
Due to the complexity of a cross-platform support, a locale aware sorting is guaranteed on Unix-like operating systems only.
Windows support added in ver. 0.7.6


Module repository


Sergey Yurzin,


Copyright (C) 2017 by Sergey Yurzin

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.18.2 or, at your option, any later version of Perl 5 you may have available.