(import 'java.util.regex.Pattern)
(def my-set #{"foo.clj" "bar.clj" "baz.clj"})
(defn set->pattern-str [coll]
(->> coll
(map #(Pattern/quote %))
(clojure.string/join \|)
re-pattern))
(println (set->pattern-str my-set))
KGltcG9ydCAnamF2YS51dGlsLnJlZ2V4LlBhdHRlcm4pCgooZGVmIG15LXNldCAjeyJmb28uY2xqIiAiYmFyLmNsaiIgImJhei5jbGoifSkKCihkZWZuIHNldC0+cGF0dGVybi1zdHIgW2NvbGxdIAogICgtPj4gY29sbAogICAgKG1hcCAjKFBhdHRlcm4vcXVvdGUgJSkpCiAgICAgIChjbG9qdXJlLnN0cmluZy9qb2luIFx8KQoJICAgcmUtcGF0dGVybikpCgoocHJpbnRsbiAoc2V0LT5wYXR0ZXJuLXN0ciBteS1zZXQpKQ==