I wonder why would a C++, C#, Java developer want to learn a dynamic language?
Assuming the company won't switch its main development language from C++/C#/Java to a dynamic one what use is there for a dynamic language?
What helper tasks can be done by the dynamic languages faster or better after only a few days of learning than with the static language that you have been using for several years?
Update
After seeing the first few responses it is clear that there are two issues.
My main interest would be something that is justifiable to the employer as an expense.
That is, I am looking for justifications for the employer to finance the learning of a dynamic language. Aside from the obvious that the employee will have broader view, the
employers are usually looking for some "real" benefit.
Philosophical issues aside, I know that I have gotten value from writing quick-and-dirty Ruby scripts to solve brute-force problems that Java was just too big for.  Last year I had three separate directory structures that were all more-or-less the same, but with lots of differences among the files (the client hadn't heard of version control and I'll leave the rest to your imagination).  
It would have taken a great deal of overhead to write an analyzer in Java, but in Ruby I had one working in about 40 minutes.
Why learn Perl, Python, Ruby if the company is using C++, C# or Java as the application language?