Back in the dialup days, my modem was plugged into a homebrew Linux firewall/router so that I could use the Internet from multiple machines at once. Which outside of a large business or college campus, was considered pretty much advanced wizardry back then. The problem was that I had one phone line and couldn't tie it up all the time. I wanted to be able to open a program on the desktop of another computer, click a button marked "connect to internet" and have that talk to the server to start the dialup process. And then also a "disconnect" button to hang up later. With a little text box to show any errors and whatnot. There were some half-solutions to this in existence at the time, but nothing that fit my exact use case.
I had been beating my head against various Perl experiments which weren't getting me anywhere until finally someone on IRC said, "oh, have you tried Tcl/Tk?"
Tcl was so easy to learn that I had a working proof of concept by the end of the day. Another couple of days to tidy it up. Used it daily for a few years until DSL came to my area.