I'm a huge fan of both Perl5 and Scala. They are both strong language that fill different niches. In my opinion—and I know many won't agree—, when building complex class hierarchies, static typing is a must have. Thus I only use Perl for simple tasks: command-line one-shots, file manipulation, an audio player… and keep Scala for more complex things.
Scala is basically Java on steroids.
- Since both compile to the same .class, they are entirely interoperable (Java code calling Scala functions sometimes requires boilerplate, but the other way round is trivial). This is a huge advantage, considering the vast amount of Java library available.
- Scala's syntax is great and flexible. You can define your own operators; define objects that can be called as functions (this is a common pattern in Scala, even array accesses are written array(index)); use OO, functional, procedural or mix everything… Yup, in Scala too, TMTOWTDI.
- There is no performance hit for using Scala rather than Java. On the contrary, using functional idioms is usually faster in Scala, because they are specifically optimized (e.g. tail recursion).
- The only thing I don't like about Scala are the compilation times. It's getting better, but they where really silly (about 10s for 1000 lines on my machine).
I hope this was helpful (: