These small utilities allow creating very lightweight job queue systems
which require no setup, maintenance, supervision, or any long-running
processes.

The intended purpose is ad-hoc queuing of command lines (e.g. for building
several targets of a Makefile, downloading multiple files one at a time,
running benchmarks in several configurations, or simply as a glorified
`nohup`), but as any good Unix tool, it can be abused for whatever you like.