Deferring the execution of a command

More than once, I have found myself running a program that calls a given script multiple times, and sometimes, way too many times. In some cases, for instance, it was only necessary to run the script once in one minute, instead of hundreds of times.
Sounds like I want something like dpkg's deferred triggers, right? pretty much so.

With this need, deferred-run was born. Example:

$ deferred-run -l lock -- echo hello world
$ deferred-run -l lock -- echo hello world
$ sleep 3
$ deferred-run -l lock -- echo hello world
[some seconds later...]
hello world

In spite of multiple calls, echo was only called once.
Best part, it only requires sh and flock.

If you are interested in shell trickery, you should take a look at its code.