I guess Perl should be spelled in all caps, PERL like FORTRAN, they are both acronyms

From whats the difference between "perl" and "Perl":

perl is not an acronym

Though there are several backronyms in use, please note that Larry originally chose the name "Perl" -- after going through every single word in the dictionary! -- arbitrarily for its positive connotations. Actually, he originally chose "Pearl", but that name was already taken.

From the draft Oxford English Dictionary entry cited on history.perl.org:

Perl Brit.
Perl, perl, irreg. PERL
Computing.
perl n. ,
arbitrarily chosen for its positive connotations, with omission of -a- to differentiate it from an existing programming language called Pearl. Coined by Larry Wall in the summer of 1987; the program was publicly released on 18 December of that year. Acronymic expansions of the name (such as Practical Extraction and Report Language and Pathologically Eclectic Rubbish Lister), though found in the earliest documention for the language, were formed after the name had been chosen. Coinage details confirmed by personal communication from L. Wall, May 2000. A high-level interpreted programming language widely used for a variety of tasks and especially for applications running on the World Wide Web. The form Perl is preferred for the language itself; perl is used for the interpreter for the Perl language.