http://www.perlmonks.org?node_id=480429


in reply to problematic OO

I'm not OO Perl guru but in constructor (new sub) You declared $self as hashref but seems to me that You never initialize referred hash. All items like $self->{SUBJECT} or $self->{SUBJECT} are always undefined because You never assign something to them.

Then when calling You should do
PL::Mail->new();