When I was a grad student I was doing biomolecule calculations using a program I'd written in Perl. But as the molecules got bigger the programs began taking too long, so I switched to C++, and was amazed (since I didn't have a lot of real-world experience working with interpreted vs. compiled languages at the time) that C++ was literally 50x faster. I would actually have preferred using Fortran, but the program needed to dowload biomolecule info. from an NIH database, and also run a few external programs and capture their output. And (at the time) Fortran couldn't do one or both of those (I forget which).