[galaxy-dev] Using operations on multiple datasets

Sorry for the crosspost to Biostars, but I didn't get a response, so I thought I'd post here: I just noticed that Galaxy allows creation of lists of datasets by clicking on the "Operations on multiple datasets" in the history panel. How does one use this with a custom tool (e.g. what does one put between the <input> </input> tags). Is the list treated as a text file with a list of each file? I couldn't find any examples or documentation online. I'd appreciate it if someone could point me in the right direction. Thanks!