Support for LET() (Excel) or VAR() (PowerBi) style function

[brad302]

I think a function that works the same as those two aforementioned ones for the given product would be incredibly handy.

Sometimes, we want to do things in a single expression rather than using multiple operations and without the ability to re-use a defined, in memory, in calculation variable in an expression makes for a very verbose and unnecessary approach.

e.g. I may want to define an array and perform additional operations over that array and then act on the results before outputting it in a Compose or Set/Initialize Variable operation.

let(
  _text, ';test1;;test2;;test3;test4;;test5;test6;test7;test8;',
  _replacedText, replace(_text, ';;', ';'),
  _arrayOne, split(_replacedText, ';'),
  _arrayTwo, if(equals(first(_arrayOne), ''), skip(_arrayOne, 1)),
  _arrayThree, if(equals(last(_arrayTwo), ''), take(_arrayTwo, sub(len(_arrayTwo), 1))),
  _result, _arrayThree,
_result
)