#!/usr/bin/perl
use strict;
use warnings;

my $basedir='/path/to/files/';
my @filelist=qw(irgenwas12 irgenwas34 irgenwas56 irgenwas78 irgenwas90);

for my $file (@filelist)
{
  my $date='';
  my $name=$file;
  open(my $fh, '<', $basedir.$file) or die("ERROR open $basedir$file ($!)\n");
  while(my $line=<$fh>)
  {
    ($date)=$line=~/^\{datestamp=(\d{12})\}/);
    last if($date);
  }
  close($fh);

  $file={name=>$name,date=>$date};
}

@filelist=sort{$a->{date} cmp $b->{date}}@filelist;

for my $file (@filelist)
{
  print $file->{name};
  print $file->{date}?' ('.$file->{date}.')':' (NO DATE FOUND)';
  print "\n";
}