This example demonstrates how to merge event pools using the dedicated o2-generators-merge-evtpool. The pools to merge are listed in pools.txt. They can be local files or alien:// paths, and a line can also point to another local file list. AliEn pools are read directly from the storage elements, so a valid alien token is needed. The merged pool is an ordinary evtpool.root file (by default), so it can be used with the evtpool generator.