#!/usr/bin/perl

use strict;
use warnings;
use Tie::File;

my $file_one = 'Datei1.txt';
my $file_two = 'Datei2.txt';

open my $fh, '<', $file_one or die $!;
tie my @lines, 'Tie::File', $file_two or die $!;

while( my $line = <$fh> ){
    chomp $line;
    my @words = $line =~ /\b([A-Z].*?)\b/g;
    for my $word ( @words ){
        unless( check( $word, @lines ) ){
            push @lines, $line;
        }
    }
}

untie @lines;

close $fh;

sub check{
    my ($value) = shift;
    for my $line ( @_){
         return 1 if $line =~ /\Q$value\E/;
    }
    return;
}