A convention I've seen on github for project names, if not script/app names, is “p5-”. I don’t think I’ve personally ever used a prefix in any other way, and rarely even use the “.pl” suffix. If there is a name clash, I just pick a different name. I don’t expect to see “perl” or “p” or “pl” in the name unless it’s something like a2p where the name/language is part of what the code does.