I've worked with SunCluster, MC ServiceGuard and Veritas Clusters. All three allow/require scripting - and that can be done in Perl as easily as in any other language. Some of the Veritas software is actually written in Perl. I remember doing a Veritas training and we wanted to do something that wasn't supported (a postshutdown hook I think). I impressed the trainer by hacking the Veritas software and adding the feature we wanted - just 2 lines of Perl.

Abigail