After a Wheezy to Jessie upgrade I also get the error: defined(@array) is deprecated at /usr/share/perl5/Mail/Sender.pm line 318.
Problem fixed override Sender.pm from cPan (version 0.8.23) I make a test package with version 0.8.23 (15 Jul 2014), here DSC http://open.rhx.it/debian/pool-jessie/libmail-sender-perl_0.8.23-1.dsc please consider to upgrade package last upstream release seems Mail-Sender-0.903 HTH Alessandro - Lota
