[Nagiosplug-help] Web interface shows UNKNOWN although Perl plugins return exit code 0

[Christoph Haas]

Dear list...

I am currently migrating from Nagios 1.x to 2.6 and want to take my
collection of self-made Perl plugins with me. (I was pointed at
nagiosexchange on IRC but the plugins I was interested in were either
Windows-only or written in PHP or didn't compile or were evily insecure
so I decided to stay with what I did already so I can blame myself.)

The plugins generally work well. They print out the status line as they
used to and return the exit code 0 (tested with "echo $?" on the bash).
However the web interface of Nagios shows them as "UNKNOWN" in yellow.

I read through
http://nagiosplug.sourceforge.net/developer-guidelines.html but couldn't
find anything I'm doing wrong. The plugins have served me well over the
last years. I run them with "-w" and "use strict".

Any hints how to debug that? Thanks in advance.

 Christoph