The actual error is (with perl 5.14.2 and Modern::Perl==1.20120130): [Fri Jul 20 16:37:07 2012] koha_perl_deps.pl: Use of uninitialized value $version in numeric lt (<) at /usr/local/share/perl5/Modern/Perl.pm line 25. [Fri Jul 20 16:37:07 2012] koha_perl_deps.pl: Use of uninitialized value $version in numeric lt (<) at /usr/local/share/perl5/Modern/Perl.pm line 25. As Jonathan Druart pointed out in bug 7368, it is caused by the way this module handles version numbers. So it seems like an error in Modern::Perl although its docs state that it is not necessary to pass a version or a year to Modern::Perl. AFAIK we are not passing numbers to Modern::Perl in our Koha use statements. But when I test that in a simple script, I do not even raise this warning. What makes koha_perl_deps do raise that warning?
The $pkg->VERSION check on module Modern::Perl itself generates the warning for older versions of this CPAN module. The latest version 1.20140107 contains this line now: return $VERSION unless defined $version; And that will resolve it. Note checking $Modern::Perl::VERSION ($pkg::VERSION) in the old situation would have been fine too. Closed.