Tcl is certainly not a toy language. I was introduced to it when running an eggdrop bot in the irc days, and I suspect for many of us was one of the first more feature complete languages we had no choice but to learn because we wanted to add custom functionality to our bots. I haven't kept up with it and enjoyed seeing there's still those who find it productive
Well, back in those days (around 1998-2002), when I was a kid at school, Eggdrop bots were a bit slow, which often became an important factor on channel wars: channel overtakes, net splits, and so on. So we (some friends and me) created our own bot (with a very simple DSL) just for fun in pure C, and it was very fast ( http://davis.sourceforge.net/ ). Of course, our DSL was never as well designed as Tcl.
Tcl in some ways was the cause of, and solution to a lot of problems on IRC.. I ended up becoming friends with some of the people who'd try to takeover a channel I might be in and we'd realize we had more in common than not, such as how to customize those damn bots. Still have some of those friends years later, and I'm not sure if I'm the only one. Tcl feel good story.