SPUG: Old biased arguments against defined-or operator

[Yitzchak Scott-Thoennes]

As promised at the meeting, here're the arguments advanced against the
defined-or operator (orignally proposed as ??, hookhook, now //) that
delayed it for so very long.

Watch out for the strawmen; they come on thick and fast:

http://www.perl.com/tchrist/defop/defconfaq.html
http://www.perl.com/tchrist/defop/defprofaq.text