Running 'prove t/ImportBatch.t' outputs the following message: t/ImportBatch.t .............................................. 1/3 Use of uninitialized value in concatenation (.) or string at /usr/local/share/perl/5.20.2/MARC/File/XML.pm line 399, <__ANONIO__> chunk 1. Use of uninitialized value in concatenation (.) or string at /usr/local/share/perl/5.20.2/MARC/File/XML.pm line 399, <__ANONIO__> chunk 1.