Certainly factor/retroforth, Forth is too low level to be useful, but with support for quotations and streams, factor/(retro?) might be good, dealing with series a la rebol is also a good idea. Unfortunately all of those languages are kind of dead.
The interesting thing is that pipes behave in an rpn like fashion, but standard behavior is prefix based, So a rebol like language should be the normal operation, and then it changes to rpn when you pipe, the only languages I see implementing this is rye, which is highly experimental.
Powershell is also a really good option, at least for what OP wants, I like terseness. I can read bash code fine enough, until someone starts golfing, but that's true of all languages. python also has xonsh.
The interesting thing is that pipes behave in an rpn like fashion, but standard behavior is prefix based, So a rebol like language should be the normal operation, and then it changes to rpn when you pipe, the only languages I see implementing this is rye, which is highly experimental.
Powershell is also a really good option, at least for what OP wants, I like terseness. I can read bash code fine enough, until someone starts golfing, but that's true of all languages. python also has xonsh.