With the latest version of Perl, there is the following error in C4::AuthoritiesMarc::FindDuplicateAuthority: Useless use of '\'; doesn't escape metacharacter '(' at /home/jcamins/kohaclone/C4/AuthoritiesMarc.pm line 856. That doesn't seem good.
This is due to unnecessary escapes inside a bracketed character class. Locate C4/AuthoritiesMarc.pm (for me it was in /usr/share/koha/lib) and replace line 856 containing this: my $filtervalues=qr([\001-\040\!\'\"\`\#\$\%\&\*\+,\-\./:;<=>\?\@\(\)\{\[\]\}_\|\~]); with this: my $filtervalues=qr([\001-\040!'"`#$%&*+,\-.:;<=>?@(){}\[\]_|~]); (See 'man perlrecharclass' under the section 'Special Characters Inside a Bracketed Character Class'.) I raised this to medium importance due to getting flooded with cron emails every 5 minutes. And if nullmailer is not configured immediately after installation, log files will grow to enormous sizes. (In just a few weeks, my logs grew to well over 10GB and I ran out of disk space.)
*** This bug has been marked as a duplicate of bug 12654 ***