logging a function's argument

[StephenG1CMZ]

I have previously included an assignment within a return statement.
Something like
return lst:={1,2,3}
Which both assigned the list to lst and returned the list.

Which makes me wonder whether something like
Fun(lst:={1,2,3})
Might help if you can call fun with a list.

Or perhaps
Fun(lst(0):=1,lst(0):=2,lst(0):=3)
Instead of fun(1,2,3)?

(the lst(0) syntax keeps appending to lst)