Because reliable programs should belong to more than just Dijkstra.
guarded-commands is a Common Lisp port of my favourite Perl module Commands::Guarded. It provides similar functionality using a similar API.
guarded-commands is available on github.
See the README for more information, or the tests.lisp file for examples.
My e-mail address is email@example.com. Questions, comments, patches, beratings, and bug reports are all welcome.