I use a perl script to format the error output of my compiler in a way that can be easily parsed by the error list. This worked fine up to version 1.9 of the error list (which I still use today).
With the more recent versions (since the german localization, 2.0 ?) I get a very strange behaviour: I check the error output in the plugin options and get a display of all included errors and warnings. But in real life, the error list shows just nothing. I have tried to modify my perl script in several ways (output to std out, output to error out, output to both) without any change.