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.
The "real benefit" that an employer could see is a better programmer who can implement solutions faster; however, you will not be able to provide any hard numbers to justify the expense and an employer will most likely have you work on what makes money now as opposed to having you work on things that make the future better. 
The only time you can get training on the employer's dime, is when they perceive a need for it and it's cheaper than hiring a new person who already has that skill-set.
Why learn Perl, Python, Ruby if the company is using C++, C# or Java as the application language?