Worked like a charm. The following allowed me to write different codes for Xenon and Boron in the same file:
#if (PLATFORM_ID == PLATFORM_BORON)
// Stuff for Boron
#else
// Stuff for other boards
pinMode(PWR, INPUT);
#endif
Also, I had some trouble with digitalRead(PWR) until I realized that it needs pinMode(PWR, INPUT); in setup() to work, per Mesh (Argon/Xenon) detecting USB power loss .
Everything is working well now. I really appreciate the fast and spot on help in this forum - thanks again.