The phrase "foo programmer," where foo is a programming language, usually means "someone who writes programs in foo." But the phrase "Perl programmer" implies much more than, say, "C programmer" or "FORTRAN programmer" or even "assembly language programmer." You see, Perl programmers like to code in Perl. They like to code in Perl like they like to breathe. This love of the language (some would call it a dependency) leads to strange behavior, and one of the first symptoms is the desire to write a JAPH. JAPH stands for Just Another Perl Hacker, and refers to a humorous little Perl program which prints "Just Another Perl Hacker" through trickery and/or magic (of course, the humor will be lost on anyone but a Perl programmer). In fact, the behavior exhibited by Perl programmers may also be the result of trickery and/or magic: statements made by Perl's creator Larry Wall, some of which appear as comments in his code, evidence attitudes often found in Perl programmers. Perhaps Larry transmits these personality traits magically through Perl...
Are you a Perl programmer? There's only one sure way to find out: take the Perl Purity Test. And if you turn out to be purer than you thought, don't worry. Go write a JAPH or ten, and your score is bound to improve.