my %files;

read_files(\%files,'dir1');
read_files(\%files,'dir2');

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

for my $file (@sorted)
{
  my @paths=map{$_.'/'.$file}@{$files{$file}};

  # mach was mit den Pfaden
  print "FILES: ".join(' , ',@paths);
}

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->{$file}},$dir1);
  }
  closedir($dh);
}