The tool allows users to tune it by using the "--engines" (or "-e") command-line
switch to "specify a comma-separated list of search engines", according to the
manual. The list, however, is nowhere to be found.

The manpage mentions "Sublist3r enumerates subdomains using many search engines
such as Google, Yahoo, Bing, Baidu, and Ask. Sublist3r also enumerates
subdomains using Netcraft, Virustotal, ThreatCrowd, DNSdumpster, and
ReverseDNS", but that does not mean those are the valid keywords for them
(although they seem to work).

It would be great if the author could provide a listing of available engines,
possibly indicating which are active by default.

Thanks!