Java's OO is generally cleaner than Perl's, at least from the point of view of the language itself (the API, OTOH, has turned into an unmaintainable mess of broken classes that were replaced with brand new classes instead of fixing the orginal problem). Inheirtience, in particular, works a lot better (inheritience is so clunky in Perl5 that some people say you should avoid it completely).

As for overall language comparisons, it's hard to find objective comparisons between Perl and Java, but you can dig up plenty of flame wars.

IMHO: When I was first learning Java, I thought I had finally found the closest thing to the One True Language I could ever hope for. And indeed, the language structure and object system is very clean. However, the API is so annoying that it elimnates any benifit the underlieing language would have given you. And don't get me started on AWT and Swing.

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I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated