Infinitely long phrases are one of my concerns with Parse::RandGen, but I might be able to do something about that. I'd really like a module that would handle a regex like /Hello\s{1,3}world.*/ by outputting:

Hello world [and any text that follows]
Hello  world [and any text that follows]
Hello   world [and any text that follows]
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Kind of a compromise between YAPE::Regex::Explain and Parse::RandGen. Then, I would just eliminate the phrases with multiple spaces and explain in a footnote that multiple spaces between words would match. I guess I have very specialized needs and I expect to have to customize the modules.