fetch-ocsp-response is a Perl script to perform OCSP query and get response. It uses openssl command under the hood. nghttpx uses it to enable OCSP stapling feature. fetch-ocsp-response has been developed as part of h2o project (https://github.com/h2o/h2o). The script file with the same name in this directory was copied from their github repository. fetch-ocsp-response is usually installed under $(pkgdatadir), which is $(prefix)/share/nghttp2.