Running

bufrextract.pl sn.0113.bin --ahl "^IOB" --outfile iob.dat

will extract all BUFR BUOY messages from the file sn.0113.bin of GTS bulletins into iob.dat, whose content can be checked with bufrread.pl, see excerpt here. This might be compared with the corresponding output giving for bufrread.pl --ahl.

Adding --without_ahl in the command above will lead to the obvious change of not including the AHLs in iob.dat

While if the BUFR file contains complete GTS bulletins, adding --gts (instead of --without_ahl) will result in the full GTS envelope to be included, see the Manual on the GTS for details.