I would say that each language is better for something (even though a problem can be solved in any language).
Also, one advantage in Perl is that it can be modified on the fly.
Say for example, if it is written in Java, you would have shipped the class files to your client. If there is a bug and you want to fix it at site (not that you will be allowed to do it in all cases), you can't do it. You have to check it out from your repository, make changes, compile, build and ship the class files to the client site in order to fix the bug.
If it is written in perl, you just edit it, make changes, and run it!

Also if you know several languages, you could look at the problem and say "language Y is probably the best candidate for this problem"