plugin and perl GPG modules issue

Hi all

I experience a strange issue -

I have some existing and working perl code which uses GPG::Mail and
GPG::Interface beside others.

Now I incorporated part of this code into a custom plugin.
All the GPG stuff does not work in the plugin, each gpg call returns just
null.
I checked the user it runs under as well as the gnupg homedir etc - no
success.

Are there any constraints in the qpsmptd plugin architecture regarding gnupg?
Any idea why this is not working?

I appreciate any hint on this.
Best,
Mike