I am not familiar with and I have never used this language. While the topic is interesting to me (e.g. if someone wants to brief us on the Inferno technical limitations), it is not interesting from the job finding perspective.
Again, check out the itjobswatch.co.uk
programming languages list. Limbo is not on it. What's on it - SQL, JavaScript, C#, Java, Python, PHP, C++, Ruby, T-SQL, C, some shell scripting, and then more programming languages. Without pretending to be competent in all those fields, I will go out on a limb and claim that those are used in (using the same comma separated order) web services and business intelligence, web presentation layer, Windows programming, personal computing and embedded applications and fat web clients, system administration and server end programming (and anything under the sun really), server end again, performance sensitive applications, server end yet again, same as SQL for MS SQL server, low-level programming and open source. You should decide what excites you, look at the job market to determine whether the demand and salaries for your chosen field are satisfactory, and start messing with stuff.