sub datei_lesen($)
{
   # pick parameters
   my($file) = @_;

...

       # key equals the first tract
       my $key = shift @tracts;
       my $val = [@tracts];

       # push data
       # HIER die Zuweisung ersetzen
       $data{$key} = [] unless exists $data{$key};
       push(@{$data{$key}}, $val);
   }

   # close file
   close($fhIN);

   # return data reference
   return \%data;
} # datei_lesen