The bundle provides two packages: commado and filesdo. The package commado provides the command \DoWithCSL, which applies an existing one-parameter macro to each item in a list in which terms are separated by commas.

The package filesdo provides the command \DoWithBasesExts, which runs the single parameter command on each file whose base and extension are provided through two comma-separated lists.

These loop'-like commands are (themselves) entirely expandable.