I would definitely be looking for other work, but not because I could no longer use Perl. I can see a few reasons why a company might say "Ok, we're going to build everyting in one standard language that does everything we want", and I can see choosing Java.

What I can't forgive is spending vast amounts of money and programmer time to port perfectly functional tools to a different language. I can see a mandate of "wherever we get a chance, move the old tools' functionality into new tools in the standard language", but not a massive porting effort.

So, I'd look elsewhere from a standpoint of not liking to work for management who are that arbitrary. It's nearly always a bad sign.