in reply to
How to use a .pm file in a .pl file in another directory.
Your original question seems to be answered, but
maybe this would be an opportunity to re-factor your project into something
that is a little closer to common Perl project structure? Doing so would allow
you to profit from existing tools that support building, testing, packaging, installing, etc. modules.
First step would be to move your modules into lib,
move your tests into t, and rename tests *.pl to *.t.
If you're already using Test::*, running prove -l should be sufficient to run the test suite. Another approach would be to let something like Module::Starter
create an initial directory structure including all the templates and standard files.
The latter approach might be a little bit more work concerning importing an
already existing project, but I assume it will pay off in the long run.
See also Test::Simple, Test::More,
(chose Module::Build or ExtUtils::MakeMaker),
maybe Dist::Zilla. Meditation: RFC: How to Release Modules on CPAN in 2011