. will be the last element of @INC which means that all though it will always be checked, it will be the last path checked for any modules.
if you call 
use lib '.';

[download]
. will be unshifted onto the front of @INC which means it will be checked first so you know that any modules in the current path will take precedence.

In reply to Re: Utility of "use lib qw{ . }" ? by Lachesis
in thread Utility of "use lib qw{ . }" ? by deprecated

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