For beginners, just use the CL-PPCRE . It is fast, reliable and stable, and works great with any implementation.
There's also a little trick to make working with it more enjoyable - adding a RE alias in addition to PPCRE .
(rename-package "CL-PPCRE" "CL-PPCRE" '("PPCRE" "RE"))
So, you can use it as follows: (re:scan ...
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