You should use use lib '/path/to/blib' not use '/path/to/blib/lib' if i understand you correctly.

So the argument to "use lib" should be the directory containing both "lib" and "arch".

update: or maybe you should move the whole "arch" directory into the "lib" dir. I'm not sure.

update 2: after inspecting the code in blib I assume what you actually need to do is:

use lib "/path/to/blib/lib";
use lib "/path/to/blib/arch";
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