You shouldn't have used use mylib; if you use use mylib::json; and if the module uses package mylib::json;, correct.

You shouldn't have used use lib in modules. If you got that far, Perl already knows where modules can be found.

You shouldn't have used use lib '.'; because the current work directory isn't guaranteed to be the script's directory. You should be using

use FindBin qw( $RealBin );
use lib $RealBin;
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