I posted a working version of THCB in the Code Catacombs, which uses halfcountplus's suggestion w/ the Ctrl-C interrupt. I am still surprised there is no/no one provided a simple way to just "channel STDIN->TNOUT". ikegami also suggested

open2(*TNIN, '<&STDIN', "telnet desert-island. dynodns.net 4040");
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Which actually works, except that STDIN then seems to become divorced from keyboard input at a certain point. Frankly, after much tooling around with IO::Select and what have you, i am suspicous of ikegami's ideas here in general. But if anyone can demonstrate them working in THCB, I'd love to see it!