When importing records with bulkmarcimport.pl -b, records that have a ISBN field, but not a value in subfield 'a', return an uninitialized value error on line 209. This occurs when there is a 020, but not a subfield 'a' (or 010 in UNIMARC). This occurs during the '-' scrubbing section of the script, and may or may not block the import of the record (further testing required). Since not having a 020a (or 010a in UNIMARC) does not invalidate the record, import should succeed, and the import status display should not be interrupted with this error message.
The patch I sent for bug 5067 solve also this one
Marking resolved fixed as per Frederic's comment. Please reopen if the problem is not solved.