If you put a million monkeys at a million keyboards...
If you put a million monkeys at a million keyboards, one of them will eventually write a Java program.
The rest of them will write Perl programs.
This is another programming joke. In this joke, the jokester is poking fun at the programming language Perl. There are a lot of jokes about the Perl programming language, because the Perl programming language is recognized as a very hard language to read, and a very easy language to write.
Often I have tried to read Perl programs and been unable to, because there are so many ways to do everything in the language that I can never remember them all.
This joke references the common English phrase "An infinite number of monkeys with keyboards will eventually produce the works of Shakespeare", which basically says that random chance can cause anything to happen if given enough time.
This joke corrupts the phrase and says that random noise can be interpreted as Perl.