Modules in Perl are either Object Oriented, in which case they don't export and your code does not import any function, or they are procedural. In which case you use some of their functions as function.

If you use the default import of several procedural modules that all export many function, you might end up importing two different function, doing different things, but having the same name. In which case you will see a seemingly unpredictable behavior in which case the order of import will decide which function is in use.

Being explicit about what you import can greatly reduce this risk, and the maintenance programmer (you know, the proverbial psychopath, who knows where you live) will praise your name.

So how to make sure you don't forget to explicitly import functions?