Tests acting differently inside or outside CPAN

Hello

I have a module (Text::BibTeX) that is cleanly installing when using 
cpan, but fails two tests when I try to install manually, using 
Strawberry Perl.

The tests are using a C library, getting the results through XS, and 
converting them to UTF8. From three tests that use this behavior, only 
two have that problem :-S

Is there any kind of variables or environment set by CPAN that can be 
causing this behavior?

Thank you for any hind (and yes, I know this description is too vague, 
but I am not able to explain what is going on in a btter way).

Thanks
ambs

-- 
Alberto Simoes
CCTC-UM / CEHUM