newRPL: Adding string processing commands?

[compsystems]

"Hello Earthlings" =)

1: a function to covertir in algebraic expression

"A+B+12" -> 'A+B+12'

another en RPN

"A+B+12" -> "A B +12 +"

2: expand the function of the operator |

'X+3|(X=6)' EVAL 9

"X+Y"|("X"="W") -> "W+Y"

3: get with [] or ()

"X+Y"[1] -> "X"

"X+Y"[2] -> "+"

"X+Y"[3] -> "Y"