As I'm working in perl, I keep trying to build things that do that. I'm dumb enough to build a class and forget to override that one rarely called but vital method. So, I like things that yell at me during compile time

Well, it won't yell at you during compile time, but I wrote Class::Interfaces for just this thing. However, a couple of things to note about Java-style interfaces in Perl.

• Perl does not do type checking¹, so all interface polymorphism you do has to be done manually
• Perl allows a high degree of runtime manipulation, so even if you do check the interface at compile time, there is no guarentee it won't get mucked with in runtime.

(1) - Some people here will tell you that Perl is strongly typed because it has Scalars, Arrays and Hashes which are themselves strongly typed. However, they also perform a number of automatic conversions (calling a list in scalar context) which can (at times) defeat the stong typing. And most relevant to this topic, Perl does not strongly type objects.