I agree with (2) and (3), and depending on your definition, (4). My company ships a large shrinkwrap enterprise application in Perl as proprietary software; the source is there and visible, but it's certainly not open source according to any common definition of the term.

(1) might or might not be a problem; I don't really know enough about the problem domain.

After working on this application (about 100KLOC depending on how you count) for the last year and a half, I think my answer is that applications for which correctness is a requirement probably shouldn't use Perl. Most other languages (Python, C, FORTH, assembly, perhaps Java or Ada or Eiffel) are much less likely to hide subtle bugs in apparently-working code. Of these, Python would normally be my first choice, since it has the best power-per-line ratio in my experience.

Perl was and is the right choice for our application, though; flexibility is less important for us than correctness and access to libraries. -- kragen@pobox.com