Very, very ++.

I tend to think there are three things Perl isn't the best choice for:

• Operating Systems
• Real-time Systems
• Embedded Systems

And even then, there's nothing strictly preventing Perl from being used in the first and last of these, it just wouldn't be the best choice.

In fact, I would go a step further to say that the really crucial aspect of Perl is not that everything is possible. That applies even more to C, and to assembler, even in my three above cases. Nothing is impossible in Perl, but the real triumph is that nearly everything is easy and painless in Perl.
That's what sets it apart from languages such as C, which I might call more powerful, in that they can perform certain tasks Perl cannot, or at least perform them better. Perl's triumph is its expressiveness, the fact that it takes a sometimes shockingly small amount of typing to perform the same task that would take hours and hundreds of lines in another language.