#!/usr/bin/env perl

use Data::Dumper;                                          # I like to
+ dump stuff
use strict;                                                # "strict" 
+and "warnings" are a best practice
use warnings;

my %encountered;                                           # We're goi
+ng to "stuff" the numbers encountered here
while (<DATA>) {
    chomp;
    while (m{(\d+)}g) {                                    # Find numb
+ers in the string one set (2019) at a time
        push @{$encountered{$1}},$_;                       # Note 1 wi
+ll occur twice in the line "1 this year is 2019 1"
        };
    };

# Dump them with a label (and file and line number) so we can verify
warn Data::Dumper->Dump([\%encountered],[qw(*encountered)]),' ';

# Print them longest first
local $"=qq{', '}; #"                                      # To make t
+hem more readable
for my $number (sort {$b <=> $a} keys %encountered) {      # Sort larg
+est number first
    print "$number: '@{$encountered{$number}}'\n";
    };

__END__
Hello, i'm 18
1 this year is 2019 1
1 2 3 - 4
[download]

%encountered = (
                 '3' => [
                          '1 2 3 - 4'
                        ],
                 '2' => [
                          '1 2 3 - 4'
                        ],
                 '18' => [
                           'Hello, i\'m 18'
                         ],
                 '4' => [
                          '1 2 3 - 4'
                        ],
                 '1' => [
                          '1 this year is 2019 1',
                          '1 this year is 2019 1',
                          '1 2 3 - 4'
                        ],
                 '2019' => [
                             '1 this year is 2019 1'
                           ]
               );
  at 11103133.pl line 16, <DATA> line 3.
2019: '1 this year is 2019 1'
18: 'Hello, i'm 18'
4: '1 2 3 - 4'
3: '1 2 3 - 4'
2: '1 2 3 - 4'
1: '1 this year is 2019 1', '1 this year is 2019 1', '1 2 3 - 4'
[download]