It is possible to create "nested pipelines", i.e. pipelines inside pipelines.

A nested pipeline is delimited by square brackets (`[` and `]`) surrounded by a space character.

There are 2 kinds of nested pipelines:

- input nested pipelines: where the result dataset of the nested pipeline is used as the input dataset for an argument of the main pipeline.

- output nested pipelines: where the output of a step of the main pipeline is used as the input of the nested pipeline in a following step. Output nested pipelines can only be used with the `tee` step.