in reply to
Re^3: How to add a file to @INC path in perl
in thread How to add a file to @INC path in perl
I change @INC at run-time all the time.
What you're probably confused about is that 'use Some::Module' normally happens at compile-time (actually it happens in a virtual BEGIN block) and that is how most people interact with @INC. However, you can defer useing modules by doing it in a string-eval, or you can use require, or do.
And there are all kinds of evil tricks you can play by putting code-refs into @INC.