Perhaps any of several reasons, I'd think. One simple reason that occurs to me is:

...
return 0;
...
1;
[download]

Why do you think we would be better at deducing the answer when you deny us nearly all concrete information about the problem?

You could try "perl -MO=Deparse Some/Module.pm" to see if the problem has been obscured by syntax. You could try "perl -del" then "s require Some::Module" then "n" until failure.