I'm giving up. I've spent hours on this, but having got it to work as a plugin with the extra variable fed in I still can't get my other installation to work - I think I'm going to have to put them on separate mod_perl servers. If you want to run several installations under mod_perl do they all have to have the same Plugins? Is it only the database that can be different?

Since I'm going to have to make changes to the core code anyway to get this plugin to work (I can't see how it can work just by using $opts), I think I'll leave everything as it was in the core code. I am disappointed. Whenever I want to make big modifications to Links and try to make use of the plugin system it seems that there is always something missing that stops it from working. Keeping track of changed core files is really difficult so upgrading the software becomes a huge chore.