There are surely "pure" Perl developers around (i.e., "pure" when they have choice to use other languages).

Nonetheless, in large corporations, there are driving reasons (not necessarily technological ones) why Java and C/C++ would be preferred over Perl.

For C/C++, it could simply be legacy reason, so many codes have been written in C/C++ in the past. Besides, few people would be blamed for writing in C/C++ per se; they might even look more sophisticated and intelligent that way.

C/C++'s also simply frighteningly fast (unless you write in assembly or machine code). If, say, you write high performance video game, C/C++ is pretty much your only practical choice.

For Java, it's the biggest marketing success for a programming language in recent history. It has two effects:

One, many corporate executives were persuaded to use Java (or VB) after reading some marketing material or some pseudo technical reviews. It's also politically safer for an executive to go with "brand name." (Perl is not a "brand name" for many business folks. You could easily tell from many corporate meetings. The expensiveness of many Java tools also help make Java a preferred choice among business folks--merely consumer psychology.)

Two, these days there're quite a bit of other-career-turn-programmer people or people who simply program on an as-needed basis, quite a few of them turned to Java (or VB) by its reputation (such as "ease-of-use," "write-once-run-everywhere," etc.). (Courses and certificate programs also help newcomers feel easier when making a career change.)

Java's "do everything in Java" culture may also help glue people to itself.

On the technical side, Java was indeed syntactically well-designed. Project managers do prefer a language that's more self-documentary and leaves less room for obfuscation, especially since it's never easy to ask every human being just to write in one style voluntarily

For Perl, there're good reasons why Perl programmers don't go "pure Perl."

Perl has a "there's more than one way to do it" philosophy. If one has this mentality within a language, it's not a surprise when they have such an attitude across language as well and therefore be more open to other languages as possible "ways" or options.

Perl also does tend to attract highly-skilled programmers (for whatever reasons). For a skilled individual, there's probably less need and desire to just stick to one language but use whatever most appropriate for the problem at hand.