running a command stored in a bash variable
If anyone else needs to do this, here is the solution I came up with:

#!/bin/bash

VM="name of my VM"
CMD="prlctl exec \"$VM\" ipconfig | grep "IPv4" | grep -m1 -o '\d\{1,3\}\.\d\{1,3\}\.\d\{1,3\}\.\d\{1,3\}'"
IP=$(eval $CMD)

#once you have the correct data in the $IP variable you can do something with it.. I initiate an ssh session, but you can do whatever you like.


I have no idea why eval is needed here.  Someone more familiar with bash will be needed to answer that mystery.