In the past I've used Perl for writing web sites (Duh!) and a major software build system used by our company. Nowadays I use Perl almost exclusively for writing one off utilities. For example a few times I've used Perl scripts to take the contents of a table in documentation for a standard like IEE-1588 and used it to generate hundreds of lines of C++ code for an embedded system. A few dozen lines of Perl can save hours of tedious work and even more hours of hair pulling frustration finding typos with debugging ICE!

I also frequently use Perl to parse results from tools like logic analyzers to find interesting events or calculate parameters that can't be derived directly from the tool's output. I use Perl in that sort of role most days.