Fed (Federal Reserve) and Mac (Macintosh) are not acronyms, just abbreviations. Perl is an acronym though. That's not to say that it should be PERL - over the y

Fed (Federal Reserve) and Mac (Macintosh) are not acronyms, just abbreviations. Perl is an acronym though. That's not to say that it should be PERL - over the years, 'Perl' has become a word of itself, but the reason it's not is different from the other examples you quote, so as a series they don't make sense. (Practical Extraction and Reporting Language, btw)