Interesting enough, Tcl was one of the past's most versatile tools. We used it in agent-oriented programming in 90's where code could move from place to place to cut data bill. Sandboxes were built for it. Tcl was also used in AOLserver and a related web framework before that became a fad. So, the author's point that Tcl is an option for high-performance event driven apps was proven when the highest traffic site in the world ran on it. I think we have something better today in about every area due to inherent properties of Tcl and labor invested in other solutions. Yet, Tcl delivered plenty in the past, apparently still can, and has potential for people using that sort of thing.

The main potential, though, is portability and future-proofing. Tcl is so ridiculously simple that it's been implemented on about every OS and architecture. That's batteries included due to all the existing code and ActiveState's development tools. People can extend live apps, run shell scripts, configure networks, and so on all using the same (or a similar) language. Any change in underlying platform just requires porting the (simple) lower layers. Makes Tcl a powerful future-proofing option if used judiciously.