A subroutine can be named or anonymous, just as an array can be named or anonymous.

Furthermore, a subroutine can include a lexical variable declared outside the subroutine if they are within the same lexical scope. (When a subroutine includes such a lexical variable it is called a closure.)

But here is the catch. Normally perl only needs to compile a subroutine once. But when a subroutine is a closure, it potentially might need to recompile the subroutine more than once in case the externally-defined lexical variable changes its value.

It is a Law of Perl that if a subroutine is both named and a closure then Perl will only compile it once. Powerful magicians like Merlyn are able to use this feature to practice Deep Mojo. For the rest of us, this feature is likely to produce unexpected results.

So what Merlyn was saying is that he suspects that the named subroutines in the code in question contain lexical variables defined outside of the named subroutines. And he is sceptical that these completions were performed with the necessary knowledge of Perl magic needed to make them work.