perl plugin: Re-get the perl interpreter after parsing each configuration option.

perl plugin: Re-get the perl interpreter after parsing each configuration option.

The current perl interpreter might change while parsing the configuration
(e.g. the first interpreter is created by the "LoadPlugin" option), so this is
to make sure that we're using the right interpreter at all times.

Signed-off-by: Sebastian Harl <sh@tokkee.org>
Signed-off-by: Florian Forster <octo@huhu.verplant.org>