The usual way to do this, is to first read the first file into a hash, basically creating a phone directory: 

open my $fh, "<", "/root/Desktop/file1.txt";
my %verzeichnis;
while (my $line = <$fh>) {
    $line =~ /RegEx/i;
    my $telefonnummer = $1;
    my $name = $2;
    $verzeichnis{lc $name} = $telefonnummer;
}
close $fh;

[download]

In a second loop (rather than a nested loop) afterwards, you would extract the name from each line, do a lookup in the hash and then write the result to a new file. At the end you can then replace your second file with the new file. 

open my $fh2, "<", "/root/Desktop/file2.txt";
open my $new, ">", "/root/Desktop/file2.new";
while (my $line2 = <$fh2>) {
    chomp $line2;
    $line2 =~ /RegEx/i;
    my $name2 = "$1,$2";
    print $new $line2;
    if( defined $verzeichnis{lc $name2} ) {
        print $new ";+49".$verzeichnis{lc $name2}; 
    }
    print $new "\n";
}
close $fh2;
close $new;

[download]

Updated a few of typos.

In reply to Re^2: Write in files by hdb
in thread Write in files by lolz

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