One of the frequent compile time errors people get from Perl looks like this: Can't locate Acme/ in @INC (@INC contains: ... )

Starting from Perl version 5.18 it will say:

Can't locate Acme/ in @INC (you may need to install the Acme::NameX module) (@INC contains: ... )

a much needed improvement, that already helps people go in the right direction.

Experienced Perl developers already know what does this mean but people with little or no experience with Perl might not understand it. Especially because instead of ... there is usually a long list of directories. In all that noise the important part gets a bit lost.

This error means your code is trying to load the Acme::NameX module, but cannot find it.

You probably have either use Acme::NameX or require Acme::NameX somewhere in your code.

In order to load this module, Perl will go over the directories listed in an internal array of Perl called @INC. In each directory it will look for a subdirectory called Acme, and inside that subdirectory a file called

If it cannot find the file, then you will get the above error.

Why Perl cannot find the module?

Either there is a typo in the name of the module (e.g. in our case the module is probably called Acme::Name), or you don't have the Acme::Name module installed.

Please also note that the names of the modules are case sensitive. So if you write use acme::name, it will not find the module Acme::Name. (And on Windows it might find it but it will still not work properly.)

If you have just installed the module, then either it was installed in a non-standard place, or it actually failed the installation.

What you can do is try to look at the output of the command you used to install the module. If you don't have that, then try to install it again, but this time pay really close attention to what is being printed.

It might say where does it fail, but if it was successful it will tell you in which directory was it placed.

Then you can try to see if it is one of the directories listed in @INC. You can get the list of directory on the command line by typing perl -V.

If, for some reason it was installed in a non-standard directory, you can change the @INC array in several ways.

On the other hand, if the module is part of your applications, then you might want to change @INC relative to your script. (pro article)

Can't locate in @INC

A very special case of this error messages is when perl cannot locate the warning module. (Although many people will call it pragmata and not module.)

Can't locate in @INC ...

I often see this very special case when I am teaching Perl to beginners. The first thing I teach is to always add use warnings; at the beginning of every script. Unfortunately in many cases people write use warning; leaving out the trailing s. So this is is just a simple case of typo.