This is a great tutorial. Special the code with Data::Dumper. This makes clear how map and sort interact. Just a minor. The code will not run as displayed. So I added a runnable example :

use Data::Dumper
   ## Build an array of anonymous arrays, 
   ## each of which contains the sort field and the original element.
   @anons = map{ [ substr( $_, 1 ) , $_ ] } qw[ A473 B659 C123 D222 E0
+01 ];; 
  my $dd=Data::Dumper->new([\@anons],[ qw(anons) ] )->Indent(2)->Quote
+keys(0)->Dump;
  print $dd;
  print '-' x 40 , "\n";  ## Now sort the anonymous arrays
  ## by comparing the extracted fields.
  @sortedAnons = sort{ $a->[ 0 ] <=> $b->[ 0 ] } @anons;;
  my $dd=Data::Dumper->new([\@sortedAnons],[ qw(sortedAnons) ] )->Inde
+nt(2)->Quotekeys(0)->Dump; 
  print $dd;
  print '-' x 40 , "\n";  ## Finally, build the required sorted array 
  ## by extracting the original elements discarding the sort fields.
  @sorted = map{ $_->[ 1 ] } @sortedAnons;;
  my $dd=Data::Dumper->new([\@sorted],[ qw(sorted) ] )->Indent(2)->Quo
+tekeys(0)->Dump;
  print $dd;
  print '-' x 40 , "\n";

The above code will show :


 $anons = [
           [
             '473',
             'A473'
           ],
           [
             '659',
             'B659'
           ],
           [
             '123',
             'C123'
           ],
           [
             '222',
             'D222'
           ],
           [
             '001',
             'E001'
           ]
         ];
 ----------------------------------------

 $sortedAnons = [
                 [
                   '001',
                   'E001'
                 ],
                 [
                   123,
                   'C123'
                 ],
                 [
                   222,
                   'D222'
                 ],
                 [
                   473,
                   'A473'
                 ],
                 [
                   659,
                   'B659'
                 ]
               ];
 ----------------------------------------

 $sorted = [
            'E001',
            'C123',
            'D222',
            'A473',
            'B659',
          ];



 ----------------------------------------
[download]

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