One thing other people have not pointed out is that there are significant differences in the way you program for Java vs. the way you program in Perl.

Perl can be OO, procedural or a mix of both. Java is Object-Oriented only!

For some people OOP will be an issue, especially for someone who is used to procedural or batch programming. They will struggle with it horribly till they figure it out. In the meantime, the code they write will be of little value in the long run and be scrapped as it's short-comings become obvious( for example stability ).

Another issue is that Java language offers little functionality; the power of Java is in its libraries. Instead of learning a language your programmers are going to be learning libraries, lots and lots of libraries and how to put them together. Once again count upon a high learning curve.

Perl is a pretty good intermediary between UNIX scripting and Java. If you can get ahold of objects in Perl, the syntax and structure is very similiar too Java. It can be vehicle to move to Java for those with an interest in the language.

Another major point I want to make, if they convince management that Java is the way to go; they might convince management they need to hire someone with Java experience rather than train current employees. There are plenty of companies that are willing to do Java development and they may convert themselves out of a job.

Note: This is not an attempting at putting down Java; converting a program to another a language based purely on its abilities is not going to be the only thing to consider. Sometimes people forget that a business is being run and people on the business side, while not looking over directly over their shoulders, are watching.

If a project is struggling because the current programmers are not coping well with a new programming language, regardless of their enthusiam for it, a company may seriously consider out-sourcing the project to someone with more experience.