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 [[bufrextract.pl_iobdat|here]]. This might be compared with the corresponding output giving for [[bufrread_ahl|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.