If you run import_patrons.pl with -v -v you mostly get informative output like this: Errors: $VAR1 = [ { 'missing_criticals' => [ { 'surname' => 'Kjelsberg', 'value' => 'PATRON', 'lineraw' => '"123445","1234","MYKOHA","PATRON","Betzy","Kjelsberg",,"F","","","","","",,,,,,,,,,,,"","" ', 'key' => 'categorycode', 'borrowernumber' => 'UNDEF', 'line' => 514, 'category_map' => 1 } ] }, But some of the output is Koha objects run through Dumper, and some of these are thousands of lines of output, about 32000 lines to be more exact. Not very useful. From the examples I am looking at it perhaps looks like this huge object dump happens only once per run, but I am not certain of that. To reproduce: - Create a patron CSV file that will result in errors, for example because the same cardnumber is used three times. - Import the file with import_patrons.pl: sudo koha-shell -c "perl /usr/share/koha/bin/import_patrons.pl --file patrons.csv --matchpoint cardnumber -v -v --confirm > /tmp/import-patrons.log" kohadev - Look in /tmp/import-patrons.log and verify there is at least one huge object dump