Marek Rouchal wrote to me with an interesting addendum to my previous post Who makes it into @INC first?. Besides the different ways to add directories, some of them also load additional subdirectories that you don’t specify.
Category: Modules
Who makes it into @INC first?
Perl finds modules by looking through the list of directories in @INC. There are many ways to add paths to that array, and although I’ve used all of them at some point, I’ve never quite thought about what happens when I use all of them together.
Remember that Perl uses the first matching module name it finds then
stops looking. It does not have a designed way to determine a best match and newest match or anything fancy. Whatever it finds first is the winner. This also means that someone could add paths to @INC and force your program to run their version of a module, even maliciously. This is something I write about in the “Secure Programming Techniques” chapter of Mastering Perl.