Programming :: Write A Bash Script That Sources Another Bash Script?

I am trying to write a bash script that sources another bash script. Essentially, I need a few lines to check to see if a certain variable is set. If not, I set it manually, and then source a scripts with that variable in the path. I wrote a test script to try it, but for some reason the last line does not work. Here is what I wrote:

#!/bin/sh
source ~setupdir/setup.shrc #just a test, this line works
echo ${#SETUP} # prints 0 if setup is not set, which it isn't
if [ ${#SETUP} -eq 0 ]
then
SETUP="~setupdir"
fi
echo $SETUP # prints ~setupdir

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