....
my $datum0 = date_extra($file);
textsformat("$entry/$file", $entry , $datum0);
           system "cat /home/dub/S/programming/perl/dp/textsformat.output >> $entry.tab";
         };
     };
     closedir(DIR);
  };
};


sub date_extra {
  my $file0 = shift;
  my $date = substr($file0, 9,6);
  $date =~ s/(\d{2})(\d{2})(\{2})/$3\.$2\.20$1/; # why this command does not work
return $date;
};

...
...