With a Perl project, you can use a tPerlRow component with the following code:

use Convert::IBM390 qw(unpackeb packeb);

@output_row = @input_row;
($output_row[field]) = unpackeb('p4', $input_row[field]);

See Convert::IBM390 documentation on CPAN about the pattern used to extract field in unpackeb function.

What is the Cobol Copybook definition of the field?

This is the copybook:

       FD  FF-DOSSIER.
       01  TVS1-DOSSIER.
           03 AAA-DATA-BASE-KEY.
             05 TAB-CODE               PIC X(1) VALUE "D".
             05 VWC                    PIC X(2).
             05 JAAR                   PIC X(1).
             05 DOCNR                  PIC X(4).
             05 FILLER                 PIC X(23).
           03 FAA-VNR-TELLER           PIC S9(3) COMP-3.
           03 FAB-POSTNR-TELLER        PIC S9(3) COMP-3.
           03 FAD-VLAG-INSCHR          PIC X(1).