The short answer is that you really have no idea.
Certainly, the presence of Moose (and of the companion “MooseX” packages) makes this type of question very ambiguous. It could mean any number of things. Which means that you basically need to apply salesmanship, and to be well-prepared with considered responses for a variety of scenarios (as well as exploratory questions to help you gage what the term actually means to them).
The “least common denominator” definition is probably a good place to start, as described in perlmod and the very-many similar perldoc documents. The notion, even in its most elementary and earliest implementations, of useing a package, instantiating a Perl object defined in that package, and of making method-calls to it. Being able to “spew the technical guts of how” to do this, is likely to be much less important than “knowing why and when” it is advantageous to do this. It is okay to speak in fairly abstract, conceptual terms during an initial interview. It is also okay to say very frankly that you need to research a concept that they bring up ... much better than trying to bluff, which never works. If they start hammering you with demands for technical-spew details regarding something that you truly are not prepared to answer, the best thing to do is to be very straightforward to the effect that
“I don’t know, but I can find out, and here is something that I do know which might be relevant...” “I don’t right-now know exactly what you are referring to, but I do know that I do know what I’m doing, nonetheless.” Don’t let anyone make you sweat or lose your cool, even if they attempt it, as they sometimes will.