#! /usr/bin/perl

use strict;
use warnings;


my %files;

my $dir_alt = 'C:\Users\alt';
my $dir_neu = 'C:\Users\neu';

read_files(\%files,'$dir_alt');
read_files(\%files,'$dir_neu');

my @sorted=map{$_->[0]}sort{$a->[1] <=> $b->[1]}map{[$_,(/(\d+)/)]}keys(%files);


sub read_files
{
  my $files=shift;
  my $dir=shift;
  opendir(my $dh, $dir) or die("error opedir $dir ($!)\n");
  while(my $file=readdir($dh))
  {
    next unless($file=~/\d+\.txt/);
    push(@{$files->{$file}},$dir);
  }
  closedir($dh);
}