Stuart,

if I were you I would also consider the %Regex.Matcher class ReplaceAll method to use.

For example:

set list = "ABC~DEF~GHI~JKL~MNO~[~PQR~]"

set matcher1=##class(%Regex.Matcher).%New("\[",list)

set matcher2=##class(%Regex.Matcher).%New("\]",matcher1.ReplaceAll("Y"))

write matcher2.ReplaceAll("N")

Istvan

For sure I do not want to return to the coding style like 

 S f="inputfile.txt" O f U f F  R l D

 . Q:l="***END***"

 . D ##class(process).Input(l)

But working with Python seems to be broadly accepted all over the globe without questioning the syntax of it. In other words: I agree with Robert. There is no perfect programming language and it is always painful to read a code written in an "unknown" language. On the other hand it does not mean that a programmer should not care about code maintainability. So what is the point? Everyone must find the balance between coding efficiency and readability. And tools are just tools helping us find the balance. 

My suggestion: create an interim XSL file and copy-paste before debugging...