I'd like to hear more specifics about why or perhaps where perl fits in as a scientific application

In a nutshell, if you extend perl (with XS) to incorporate that fortran/C/C++ code (as does PDL, Math::Pari, Math::GSL and Math::GMP for example), then you end up with something that's as easy to use as perl, but performs its tasks as quickly as fortran/C/C++.

Cheers,
Rob