At work, we use a variety of languages: perl, shell, C/C++, Java. Perl does all the heavy lifting that we don't actually ship. It generates some (actually, just as of the last few weeks, it now generates all) shell code, some C++ code, and some Java code. Shell doesn't come with a preprocessor, so we fake it in perl, as well as generating data as we do in C++ and Java. We use Java for a GUI. We use C++ for our core non-interactive engine (which the GUI also invokes). And we use shell for all the simple filesystem manipulations (and I use the term "simple" very loosely). We ship a private JVM to run Java, but no private perl, so we don't ship perl code.