Some meta-suggestions:

• Wrap your code in code tags to help make it stand out.
• If something's 'completely weird', tell us what's weird about it -- what you expected, what actually happened, and how that disagrees with the documentation.

I suspect you didn't read what use lib actually does, otherwise you'd have a better idea what it was doing. It adds a directory path to @INC to provide Perl with additional locations for modules.

I expect you want

use lib '/home/user/test-workspace/trunk/modules';
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for development and

use lib '/home/user/webpage/modules/';
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for production.