Shell Programming and Scripting

Hello,
I have something that should be very simple yet I am losing my head in figuring out how to get it to work:
I am calling a function passing a parameter, this will return a particular string, next I want to substring the returned value and break it apart.
All of this I want to do on a single line of code under ksh93.

I tried a few combinations but I cannot get it to work. Any ideas?
I suppose I am doing something improper with the brackets and/or parentheses. Here is my one liner:

Code:

new_var=${$(functionCall parametersForFunction):0:4}

I would have expected the chunk:

Code:

$(functionCall parametersForFunction)

to be the returned string from the function call executed, and include it in the substring statement, but no luck, I keep getting a parsing error.

Hope you can help, thanks

Please post the code, the command line typed complete with the exact parameter, the expected output, and what actually happened - complete with any error messages verbatim.

${xxx:y:z} expects xxx to be a variable name but $(functionCall ...) is not.

This will work:

Code:

new_var=$(tmp=$(functionCall parametersForFunction); echo ${tmp:0:4})