PS.: it also works if you concatenate strings:
 

write "my string"_stringVariable_"continue string"

In the first case you would be calling the "WRITE" method 3 times, once for each string divided by ",", and in the second you would be calling "WRITE" once with only one string that is a copy of the 3 strings combined together. 

You could also use concatenating to set a new variable:
 

Set stringVariable = " | "
Set stringsCombined = "my string"_stringVariable_"continue the string"

And then you can work with this new variable.

I.E. if you called WRITE stringsCombined, you would have as an output:

my string | continue the string

Hi @Michael Davidovich ! Thank you for the feedback. Now, let's take a look at those questions:

1- Does embedded Python support return values?
For a  short answer, yes it does. But as there are many ways to access python, there are many ways I can answer that. In fact I found it a very interesting topic to discuss and I'm working on a new article so I can cover more cases, but just to give it a taste, if you're using in IRIS a ClassMethod [ Language = python ] you can use "return ..." to finish the method and return a value, as you would after declaring a function in python.

2- 
Also, is there a well documented source for the iris Python package?

The documented source is Native SDK for Python Quick Reference. Now, if it is "well documented" you'll have to answer for yourself hahaha, but I'm working on getting more information and examples here. From what I've learned so far, the package has ways to connect from your python environment to IRIS, in such a way that you can access any methods you've created on IRIS, so I see it as a door to everything in IRIS.