~/MyPerl
    |
    |
    |__ src/
          |_ mycode.pl
          |
          |_ mypackage.pm


##</code><code>##

use strict;
use warnings;
use lib "home/neversaint/MyPerl/src/mypackage.pm";

# the rest of my code

##</code><code>##

~/MyPerl $ perl -c src/mycode.pl
mycode.pl syntax ok

##</code><code>##

~/MyPerl $ perl src/mycode.pl some_arg

Undefined subroutine &main::some_subrutine called at src/mycode.pl line 10.