Don't know it this helps, but for the last ten years I've worked as a freelance developer and have largely specialised in Perl. In that time I've consistantly earned well over the UK national average income and the only times that I've had trouble finding work is when the whole IT consultancy market was shrinking. I'm sure that others here have similar stories.

So, yes, it can be more than a hobby language. In fact I consider myself lucky that my hobby is also my job.