Also, be mindful in the course of any human conversation that the two terms might simply be used as though they were synonymous ... with none of the deep-meaning that someone else might ascribe to each.   When walking on the razor edge of meaning, be sure that the conversant is actually using the meaning that you think he is; that you are not reading too much into it.   Perl has many idioms, e.g. "perldoc perlvar" for doing and saying the same things in different ways.   Everyone has their own preference; gets used to doing it and saying it that way; might not even be aware of alternates.   So, know where they are coming from.