#!/usr/bin/perl

use strict;
use warnings;

my $file_1 = '/pfad/zur/datei.txt';
my $file_2 = '/pfad/zur/datei.dat';

{
   local $/ = "\n\n";
   open(my $fh_1,'<',$file_1) or die $!;
   open(my $fh_2,'<',$file_2) or die $!;
   while(defined(my $entry = <$fh_1>) and defined(my $entry_2 = <$fh_2>)){
      tu_was($entry,$entry_2);
   }
   close $fh_1;
   close $fh_2;
}