That's really weird, because for me, the program outputs the following:

#!perl -w
use strict;
use 5.010;

my @data = qw{
   this_5_string_12
   some_12_garbage_23
   this_5_string_8
   17
   this_5_string_23
   some_12_garbage_6
   102
   this_5_string_19
   5
   this_5_string_101
   };
my $width = 50;

say for
   map { substr $_, 54 }
   sort
   map { do {
            no warnings qw{ uninitialized };
            pack qq{A${width}NA*}, m{(.*\D)?(\d+)$}, $_;
          }
       }
   @data;
[download]

5
17
102
some_12_garbage_6
some_12_garbage_23
this_5_string_8
this_5_string_12
this_5_string_19
this_5_string_23
this_5_string_101
[download]

If I use exactly your Perl, I get the output.

If I ‘hash’ out your ‘use 5.010;’ - I get the following error message on the MSDOS screen

Bareword "say" not allowed while "strict subs" in use at ………..amonk_f_sort.pz line 28.

Using

use strict;
print "perl version $^V\n";
[download]

and the output is perl version v5.20.2

Therefore it seems it is something to do with the version of Perl being used.

It would be good to know how to change your Perl so that it works using 'use strict;" and with my current version of Perl (and I would like to know where the sorted data is stored or how I can store it in an array).