Also remember that useing a module might well execute code. There are a number of code blocks which are executed at parse/compile time, the most common being BEGIN{...} blocks. Any code in the module not within a function will also be executed at this time. Code can also be executed on process closedown inside an END{...} block.

So a module might be doing some magic without you realising it, and you do not need to explicitly call a single function to do that, use is enough.