Hmm, Perl, PHP, Ruby, probably Scala (which I don't really know) and even Java (despite many things) are probably fine for developing web applications. (Plus of course Javascript, but it is a slightly different kind of animal.)

Perl was definitely the best tool 15 years ago, today, this is debatable. The real question might be not so much the language itself, but the frameworks available in those languages. Perl has a number of such frameworks (Catalyst, Mojolicious, Dancer, Plack, not to speak about basic CGI), other languages also have similar frameworks. Look at these frameworks (Perl or other), and try to figure out what is your best bet.

I would personally go for Perl, because I know the language, but not everyone has to think the same way.