I was working at a library, and we had this wacky book accounting tool that was propietary software from the company that maintained our central computer system for us. The person who handled the software wanted an easier interface and a way to catch mistakes before sending off the accounting to the billing department, but the company was unwilling to give that away for less than quite a few grand.
That is, the handler wanted a glue tool that munged strings of text into a practical report. I had never used Perl, but i knew that's what it did best and i grabbed at the opportunity to learn a new language.
So for a week i spent my spare time at work hacking out a perl script that did those things. People blamed me, but it was really Perl that saved them thousands of dollars...