The word "Perl" (let's for a moment forget about how's it's written, whether Perl, perl or PERL), stands for Practical Extraction and Reporting Language. It's in this sense that I say it's an acronym. Could you enlighten me how that's wrong?
Re^5: PERL as shibboleth and the Perl community
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That is wrong because Perl does not actually stand for that. No more than it stands for PerfectlyPathologically Eclectic Rubbish Lister. (Which is also listed as a definition in the perl manpage.)
But to interject some complications into the picture, Perl stands for both of those more than, say, Perl's an Extremely Reliable Language. Why do I say that? Because Larry Wall has said that he thought up the previous two backronyms while trying to come up with a name for his new language, and liked the wordplay. To the best of my knowledge he hadn't thought up the one that I just listed. (Though knowing him he might have though up those and a dozen more, but just liked the other two better.) So the existence of fun backronyms is part of why the name Perl was chosen, but Perl itself doesn't actually stand for anything and was never meant to.
Update: Oops, Womeone Who Would Know privately corrected me on the backronym and verified the rest of what I said.
However, even if it was merely an acronym, the official spelling is still not capitalized—any more than "rom", "ram", "smog", "radar", "laser", "sonar", or "scuba" are capitalized now (which are all arguably acronyms, not backronyms).
More than just being a single backronym, in adding its second gloss "perl" was intentionally turned into a backronym generator. It would be interesting linguistically to categorize backronyms into those that are productive and
those that are fossilized. Certainly "perl" is still productive: "Polymorphic Existential Recursive Lambdas" is just the lastest one.