s/^(\d\d)//;
   my $record_type = $1;

...

      s/^(\d+{5})//;
      $key = $1;

...

      my @fields = /^
         (\d\d\.\d\d\.\d\d\d\d)   # start date
         (\d\d\.\d\d\.\d\d\d\d)   # end date
         (.{3})                   # category
         (.{3})                   # group
...
      /x;

...